Wow. I cant keep up with all the emails and PMs. Many asking what oils are good for what engine.
The flat tappet design of Rovers V8 puts a lot of stress on the cam lobes. You needa good cushion of oil for the lifter to ride on. The sheer rating is a measure of resistance to sheering off the oil.....On a rover engine, a min of 3.5 is needed. THe reason diesel oils have a high sheer rating is because the cam is pushing into engines with 3 times the compression of gas.
This is a topic that is tough to relay over a forum...So, as a GENERAL list...Here goes...My picks would probably be Valvoline Synpower 5W-40, Mobil 1 5W-30, Mobil Clean 5000 5W-30 (if the price is good enough) and Castrol GTX or Motorcraft 5W-20. If I couldn't get the Clean 5000 5W-30 cheap enough, I'd get whatever is cheap and ILSAC GF-4/GM 6094M approved and then some of thecheapest GM 4718M approved stuff I can find for the sludge sensitive cars that only "require" ILSAC GF-4 (there are several other ways to go including BG MOA for the sludge motors).
For European Cars: Mobil 1 0W-40 European Formula The European Valvoline Synpower 5W-40 and 5W-30(MST only, the regular Synpower 5W-30 and other Synpower do NOT cut it) Castrol Syntec 0W-30 and 5W-40 (Other Syntecs do NOT cut it)The good (European) Valvoline Synpower is very hard to find but it is a low SAPS version that reflects what future European formula oil will be. It even meets VW 505.01 TDI-PD diesel)!
For American and Japanese cars requireing special "synthetics" Mobil 1 5W-30, 5W-20 and 0W-20 are all excellent.
Texaco/Havoline and some Chevron, Shell, Kendal, Conoco/Phillips/Union, etc brands all have a pretty cost effective 5W-30 that is GM 4718M if you need something cheap just for Covettes and other GM cars that require premium oil or if you are just looking for a good oil to use for cars that "require" nothing special but could use a bit of extra protection (they are still API & ILSAC & most American & Japanese OEM approved)
You still need a "plain jane" SAE 5W-30 oil all the Chevys, Toyotas, etc. Just make sure it is ILSAC GF-4 and GM 6094M Approved
And you need an SAE 5W-20 for all those Fords, Hondas and a growing number of other cars. I think for this category should be WSS-M2C153-H (Ford Double time standard) approved as well as ILSAC GF-4. Motorcraft does not display that "double time" spec but it is real good stuff. I think Castrol GTX and Valvoline All Climate may be WSS-M2C153-H approved but check the bottle or product data sheet.
Lets look at a few at a time. Starting with Valvoline Synpower:
www.valvoline.com/products/Synpower.pdf
Notice that there are two different versions of Valvoline Synpower 5W-30. Scroll down to the bottom to find the second one (Synpower MST) with the European formula 5W-40 and 20W-50.
This dispells a bunch of rumers already. First, the standard Valvoline Synpower does not meet ANY industry standard oil service ratings that would indicate that it is significantly better than any conventional SAE 5W-30 oil. It doesnt even claim to pass the GM 4718M rating. If anyone thinks thats just because Valvoline doesnt choose to list all those ratings.......scan down to the bottom and look at how many proprietary ratings are listed on the same sheet for the other 5W-30. This is synthetic marketing magic.
The second page of this product data sheet shows an outstanding SAE 5W-30 for European cars and an outstanding 5W-40 for European cars. These are low SAPS oils with outsanding shear protection. Valvoline does not list their HTHS ratings but the ACEA approvals assure us that they are both above 3.5 (much higher than the SAE required 2.9). So, they dispell another myth. These two products are actually lower Sulfated Ash, Phosphorous and Sulfer (SAPS) and lower ZDDP content than just about anything you can buy at any price, but they also provide BETTER HTHS and extreme pressure protection than most other oil products. They are slightly lower than the ILSAC GF-4 approved Synpowers on the top page, and still provide MUCH better protection for camshafts, lifters and other components.
Lets dispell one more myth before leaving this page. Many claim that Total Base Number (TBN), tells the whole story of acid fignting capability and how long an oil will last. The oil products on the top page have a TBN of 8 and the oil products on the bottom have a TBN of 7. But, the ones on the bottom base numerous extended drain interval approvals*, and the ones on the top dont pass any extended drain interval approvals. ACEA A3/B3/B4/C3, MB 229.3, 229.31,229.5, 229.51, BMW LL-01, LL04 all include extended drain interval approval.
Now look at the product data sheet for Valvoline Durablend:
www.valvoline.com/products/Durablend.pdf
And the conventional Valvoline All Climate:
http://www.valvoline.com/products/All-Climate.pdf
The difference between Durablend or All-Climate and the European Synpower is significant and obvious. But, what isthe real difference between the page one Synpower and Durablend or All-Climate? The WSS-M2C929-A, WSS-M2C930-A and
the MS 6395M duplicate the ILSAC GF-4 approvals so there is no difference there. There really isnt much difference in ratings, but the price difference is huge.
This is a bit dated now but still a good read. The part about ILSAC GF-4 significantly proving engine valvetrain protection may not apply to older flat tappet camshaft engines.
http://home.insightbb.com/~st1100/GM_Oil_Primer.pdf
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_0W-40.asp
Mobil 1 5W-30 now also meets ACEA A5/B5 and honda HTO-06.
www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_0W-40.asp
Compare it to the Valvoline European Synpower 5W-40
And the Mobil 1 0W-30
www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil1_0W-30.asp You might think this is similar to Castrol Syntec 0W-30. Compare the data sheets and decide for yourself..........
www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_Clean_5000.asp Notice this conventional oil is API SM/CF approved. That means better acid fighting for those sludge making Chryslers and Toyotas.
www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_Clean_7500.asp
www.castrol.com/liveassets/bp_inter...local_assets/downloads/p,q/pds_syntec_usa.pdf
www.castrol.com/liveassets/bp_inter...NG/local_assets/downloads/p,q/psd_gtx_usa.pdf
www.castrol.com/liveassets/bp_inter...assets/downloads/p,q/pds_syntec_blend_usa.pdf
And here is the pennzoil full synthetic:
www.pzlqs.com/Tech/Pdsheet/DomesticMarketing/EngineOils/Pdf/PlatinumFullSyntheticMotorOil.pdf
Compare it to the Castrol Syntec, Mobil 1 and Valvoline Synpower. Does it meet any ACEA, MB, BMW or VW approvals?
www.pzlqs.com/Tech/Pdsheet/DomesticMarketing/EngineOils/pdf/SUVTruckMinivanMotorOil.PDF