Return-Path: Received: from orcrist.gandalf.cs.cmu.edu by K.GP.CS.CMU.EDU id aa20576; 26 Jun 91 11:33:34 EDT Date: Wed, 26 Jun 1991 11:28-EDT From: Charles.Krueger@ORCRIST.GANDALF.CS.CMU.EDU To: bovik@K.GP.CS.CMU.EDU Subject: Motor Oil Recommendations Message-Id: <677950090/cwk@ORCRIST.GANDALF.CS.CMU.EDU> The following is the post I made requesting info on motor oils, and a summary of the responses I received. --------------------------------------- I'm looking for reports comparing the relative merits of different brands and grades of motor oils. I'm aware that Consumer Reports had an article back in 1988, and I'd like to get additional pointers to reviews from other sources. Informed personal testimonials are also welcome. --------------------------------------- Consumer Reports doesn't say much, except to recommend using an oil rated with API Service "SG" 10W/30. --------------------------------------- From: Peter.Lee@FINE.MESS.CS.CMU.EDU Charlie, There are regular (and lengthy) discussion of this topic on rec.autos, rec.autos.tech, and rec.autos.sport, as well as the british-cars mailing list. To summarize, there is very little agreement about motor oils, beyond the following general rules: - you should always change your oil and oil filter every 3000-3500 miles despite what your owner's manual might say. - if you use a natural motor oil (as opposed to a synthetic such as Mobil-1), you should change your oil every 3-5 months, even if you don't drive 3000 miles in that period. Synthetic oils can go for a full year, but the mileage change should still be observed. - the DOT ratings (e.g., SG, SF, etc.) are very important. However, every "name brand" of oil gives at least SF rating, which will exceed the specifications of all but the most demanding vehicles (such as race cars) - favorite brands of car buffs: Castrol 20W-50, Valvoline, Mobil-1. (These are also the most expensive, unfortunately.) - many people have used Slick-50 without ill-effect, especially on well-broken-in newer cars. (Never use Slick-50 in a brand-new car.) Some report gains in mpg. However, others have reported that using it in a very old car will cause gaskets to leak (because of the greatly increased lubrication). Personally, I use Castrol 20W-50 in my british roadsters. But I don't think it's really all that much better than any other name brand. Peter --------------------------------------- From: Clark McDonald From the experience of the Afro mechanic: For small four-cylinder water cooled engines like in most of today's cars -- Castrol works best. For small air-cooled engines -- Harley Davidson Brand Motor Oil or Shell ashless aircraft oil. For V-8 engined cars and trucks and also older straigh inline six cylinder engines made in USA -- Shell makes the best I have seen. It's called Shell Rotella T. Not advertised very heavily. Great stuff. We use it exclusively in the NAVLAB. If you want to know where to get Shell by the case through the warehouse, drop me a line. --mack --------------------------------------- From: Karl Brace When my chevette had a bad carburator (rough idle), on cold days it would stall at the first stop sign after the choke turned off. Raising the idle speed made the warm idle annoyingly high. The solution was to use 5W-30 oil. It acts like 5 weight (thin) oil when cold, providing less drag on the engine. It costs a small amount more, but when I used it the problem was non-existent. In the summer it didn't matter much, but changing from 10W-40 to 5W-30 made a dramatic difference 2 winters in a row! Newer cars with fuel injection and engine computers shouldn't have this problem. My brother had an old Audi that burned 2 qts in 3000 miles when he used 10W-40, but only 1 qt using 20W-50. So if you switch to a lighter weight oil, make sure you check the level!