My 93 LWB says to use premium.
I was told use as low as possible until it starts ro run bad then go up one grade.
I was told use as low as possible until it starts ro run bad then go up one grade.
Really, What would Happen???
- Thread starter Ross_Thoma
- Start date
From How Stuff Works:
If you've read How Car Engines Work, you know that almost all cars use four-stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. (See How Car Engines Work for details.)
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.
The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.
It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.
During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:
Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).
If you've read How Car Engines Work, you know that almost all cars use four-stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. (See How Car Engines Work for details.)
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.
The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.
It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.
During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:
Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).
GregFrench said:
I guess if yours says to use premium then mine does too....Oh well, it STILL works well on regular!
A
abearly
Guest
I've always understood that it all comes down to altitude... I live at 6000 ft. and can run
"the cheap stuff" because with less air comes less need for octaine to get the best fuel/air mixture. If I lived at sealevel, I would run premium because of added amount of atmosphere. I have owned 3 discos (95,96,04) and have run 85 octaine in all three without a "knock" for years, but I can't say that you could do that on the coasts...
"the cheap stuff" because with less air comes less need for octaine to get the best fuel/air mixture. If I lived at sealevel, I would run premium because of added amount of atmosphere. I have owned 3 discos (95,96,04) and have run 85 octaine in all three without a "knock" for years, but I can't say that you could do that on the coasts...
P
parthog
Guest
A lot of information, but to me it is simple:
The truck gets lousy mileage,
the truck has marginal power.
If you use lower octane fuel, the truck will not burn it as efficiently (the whole timing thing). This will give you less power and lower mileage. I have verified lower mileage on cheap fuel in my truck, the extra price for premium improves mileage enough to pay the difference. I can't verify the power decrease it's slow either way.
LR most likely requires the higher octane fuel to achieve the marginal fuel mileage and perfomance, emissions would logically be affected also by incomplete combustion so maybe it couldn't even get the emissions numbers on regular?
As far as valve fouling, don't know I burn the good stuff and hammer it occasionally. Mine idles like a good German I-5. Premium usually also has better detergents and keep the injectors and valves cleaner, might help.
I burn the good stuff, not giving up even 1hp or 1mpg if I don't have to.
- Jeff
The truck gets lousy mileage,
the truck has marginal power.
If you use lower octane fuel, the truck will not burn it as efficiently (the whole timing thing). This will give you less power and lower mileage. I have verified lower mileage on cheap fuel in my truck, the extra price for premium improves mileage enough to pay the difference. I can't verify the power decrease it's slow either way.
LR most likely requires the higher octane fuel to achieve the marginal fuel mileage and perfomance, emissions would logically be affected also by incomplete combustion so maybe it couldn't even get the emissions numbers on regular?
As far as valve fouling, don't know I burn the good stuff and hammer it occasionally. Mine idles like a good German I-5. Premium usually also has better detergents and keep the injectors and valves cleaner, might help.
I burn the good stuff, not giving up even 1hp or 1mpg if I don't have to.
- Jeff
Interesting information on this thread.
I've been using the 87 in mine (that's the lowest in my part od So.Cal.) and all seems to be fine. I drive less than 3 miles to work, do 60 on the freeway and have not driven over 30 miles at any one time...never heard a knock.
Can you hear it on these V8's? I know the little 4 cyl. Nissan I had years ago did not like the 87 stuff...it sounded like hell! Can't say I drove that thing easy though!
Maybe I'll do the 89 or 92 for a tank ot two and see what happens. I think that's what we have here, 87, 89 & 92.
I've been using the 87 in mine (that's the lowest in my part od So.Cal.) and all seems to be fine. I drive less than 3 miles to work, do 60 on the freeway and have not driven over 30 miles at any one time...never heard a knock.
Can you hear it on these V8's? I know the little 4 cyl. Nissan I had years ago did not like the 87 stuff...it sounded like hell! Can't say I drove that thing easy though!
Maybe I'll do the 89 or 92 for a tank ot two and see what happens. I think that's what we have here, 87, 89 & 92.
My take on this thread is this...The Disco engine ECU is programed to require high octane fuel (for what ever their reasons)....
If you use a lower octane fuel, indeed the engine ECU will compensate for that but their is a downside, your trucks ignition will be continually retarded and you will generate more internal heat not necessarily shown on the temperature gauge....
This is one reason why so many of the Disco engines developed dropped cylinder liners.......low octane= internal heat based on the factory ECU settings
I know their are a lot of real knowledgeable guys on here, smarter than Land Rover engineers even....but Land Rover are correct on this issue......
If you use a lower octane fuel, indeed the engine ECU will compensate for that but their is a downside, your trucks ignition will be continually retarded and you will generate more internal heat not necessarily shown on the temperature gauge....
This is one reason why so many of the Disco engines developed dropped cylinder liners.......low octane= internal heat based on the factory ECU settings
I know their are a lot of real knowledgeable guys on here, smarter than Land Rover engineers even....but Land Rover are correct on this issue......
Here in FL several Citgos now offer 4 grades... 87, 89, 91, 93... 91 is still considered premium if I recall correctly... its about .05-.06 less per gallon if you're trying to save a buck per tank. When I use to live in NY years ago, Sunocos in NY/NJ sold 87, 89, 93, 94...
I guess even if you are filling up once a week it is only an extra buck a week and thus 52 dollars a year.
Gas is cheaper than coffee even at these prices.
Gas is cheaper than coffee even at these prices.
this thread is full of mis-information
bottom line is the the pre- gems engines can handle the low octane stuff really well.
the Gems and Bosch engines will want to see the higher octane.
using the lower octane stuff in the pre-carbon cutter valve Gems engines will cause your valves to start sticking after awhile with the only real option being a tear down and head/valve job. This is why 96 and 97 disco's got such a bad rap back in the day.
from 98 on the trade off of lower gas prices will be less performance and mileage because the resultant retarding of the spark more then off sets the difference in a effort to protect the engine.
bottom line is the the pre- gems engines can handle the low octane stuff really well.
the Gems and Bosch engines will want to see the higher octane.
using the lower octane stuff in the pre-carbon cutter valve Gems engines will cause your valves to start sticking after awhile with the only real option being a tear down and head/valve job. This is why 96 and 97 disco's got such a bad rap back in the day.
from 98 on the trade off of lower gas prices will be less performance and mileage because the resultant retarding of the spark more then off sets the difference in a effort to protect the engine.
keepitwildtv said:
It's a false economy. I track my milage carefully. My wife accidentally filled up with 87 octane, and the milage dropped from 14 to 10mpg. No detonation, but the milage dropped 30%.
But, you save 10% on the cost of the fuel right.
It's nice to know that the Rover engine *can* run on 87 octane in a pinch, but it's not cheaper.
I still find it a fucking tragic comedy that this 47hp/L engine requires high octane in the first place.
Checked my manual for shits and giggles... premium per my 04 owners manual is 90 or 92 octane... states either is considered premium... so technically 91 falls in that range, but since I'm in FL where its in the 90s 50% of the year... 93 is the better choice...
Also there is a warning in the manual not to use fuel system cleaners as they can damage gaskets/seals... doesn't list any specifics really... does say gas with detergents is good.
As stated before... gas is cheaper than coffee... bottled water... beer... even orange juice... Tropicana is still $4/gallon here in FL
Also there is a warning in the manual not to use fuel system cleaners as they can damage gaskets/seals... doesn't list any specifics really... does say gas with detergents is good.
As stated before... gas is cheaper than coffee... bottled water... beer... even orange juice... Tropicana is still $4/gallon here in FL
2
2FUELS
Guest
Just got this done Saturday, I don't have actual MPG's but for what its worth:
pre tune up 95 Disco (Bone stock 93k) on 89 octane ethanol blend = 238 miles from full until low fuel light.
Same truck after Magnecore wires, cap, rotor and Champion
RN11YC4's with 91 octane = 320 miles from full tank to low fuel light.
(the last 150 miles with a Kayak on top)
I think about 4 tanks (even at the higher $$$) will pay for the tune up...
pre tune up 95 Disco (Bone stock 93k) on 89 octane ethanol blend = 238 miles from full until low fuel light.
Same truck after Magnecore wires, cap, rotor and Champion
RN11YC4's with 91 octane = 320 miles from full tank to low fuel light.
(the last 150 miles with a Kayak on top)
I think about 4 tanks (even at the higher $$$) will pay for the tune up...
If you use a lower octane fuel that the air bags will not deploy properly killing the children in third world nations. Please, won't someone think of the Australians!
Compliments of http://www.rpiv8.com/engine-4.htm
A very good tech article on our engines.
3.9 & 4.2 The true & main reason these engines run very hot is due to the fuel/air ratio, or fuel mixture, that is controlled by the engine EFi computer (ECU Chip) from the factory. This was designed to run very lean through the mid range to make altitude driving or mid range emissions (tested in some countries) less of a problem, the upshot of this however is that when these engines are used on low quality or low octane fuels, or when the engines are upgraded with items even as minor as a free-flow air filter or exhaust headers & Cam/Head upgrades, although all of these are only mild upgrades, they will make a weak engine run even weaker and the problem will get closer!
The solution is simple (if it's not cracked already), fitting our Optimax or Tornado Eprom (ECU Chip) will give your engine the near perfect fuel/air ratio it deserves, thus giving lower engine internal temperatures and giving, without other modifications to all, 15% efficiency boost [power and economy} & also allow the upgrades you have already done to be beneficial at last, instead of being detrimental. 3.9 & 4.2 ECU info 'Click'
4.0 & 4.6 (new shape) suffer a similar but normally less dramatic problem although these engines are much stronger. The same air/fuel ratio problem will arise with low octane fuels, you will not normally suffer cracked blocks, but you will cause the liner to shift from its seat or cause sticky valve guides (partial seizure), and the solution is much the same as the 3.9 & 4.2 above, an ECU re-chip will sort it out and more
A very good tech article on our engines.
3.9 & 4.2 The true & main reason these engines run very hot is due to the fuel/air ratio, or fuel mixture, that is controlled by the engine EFi computer (ECU Chip) from the factory. This was designed to run very lean through the mid range to make altitude driving or mid range emissions (tested in some countries) less of a problem, the upshot of this however is that when these engines are used on low quality or low octane fuels, or when the engines are upgraded with items even as minor as a free-flow air filter or exhaust headers & Cam/Head upgrades, although all of these are only mild upgrades, they will make a weak engine run even weaker and the problem will get closer!
The solution is simple (if it's not cracked already), fitting our Optimax or Tornado Eprom (ECU Chip) will give your engine the near perfect fuel/air ratio it deserves, thus giving lower engine internal temperatures and giving, without other modifications to all, 15% efficiency boost [power and economy} & also allow the upgrades you have already done to be beneficial at last, instead of being detrimental. 3.9 & 4.2 ECU info 'Click'
4.0 & 4.6 (new shape) suffer a similar but normally less dramatic problem although these engines are much stronger. The same air/fuel ratio problem will arise with low octane fuels, you will not normally suffer cracked blocks, but you will cause the liner to shift from its seat or cause sticky valve guides (partial seizure), and the solution is much the same as the 3.9 & 4.2 above, an ECU re-chip will sort it out and more
I ran regular in my 01 D2, had 133k on it when totalled, never had a problem. I have a 96 D1, I run on regular, I have 235k on it, never a problem. For shits and giggles I went down to Palm Springs one time, put super in it, it's the only time I've had to drop into 3rd gear to get up The Grapevine, other times I've been on regular, pulls the whole hill in 4th and 5th. In my case with my Disco it does better on regular then super. I also checked mileage on the way to Palm Springs and it didn't make more than one iota of difference. I don't notice it runs any hotter either, I can let it idle in Palm Springs when it's 120 with the AC on full blast, drive it around the desert in the same heat and the temp guage is in excactly the same spot. Frankly my wife's Lexus is supposed to run super, too, we use regular, runs fine, the Benz we had which we put about 165k on was supposed to use super, we used regular, never a problem with that either. I could see running super if you had a 502 making 500 + HP, but frankly I don't think you need it in most cars. Now the Tundra I had which was supposed to run on regular would ping like a mofo, so I ran that on Super, go figure.