Does anyone know if MOBIL1 0w-30 is any good for a stock '02 Wrangler X? It's fully synthetic AND is suppose to provide improved fuel economy. MOBIL recommends it (of course they do!) for 5w-30 and 10w-30 applications. Also, is this 0w-30 as good mileagely as other fully synthetics (MOBIL was unclear about this)?
Im very skeptical that different oil is going to make much difference in fuel economy, especially in something as aerodynamic as our rolling bricks/barndoors. I dont know much about viscosity, but I too would stick with the factory recommendations, as the wrong oil can cause major (read: expensive) problems.
Actually you would not see a change in gas mileage. In multi vis. oil, the second number is your viscosity at operating temperatures so you would be using a 30 in either case, after your engine came up to temperature. A multi vis oil uses the low number for the base stock, 5-30 mineral oil is made from a 5 weight oil, long chain polymers are added to allow the oil to behave like 30 weight at operating temperature. One advantage of a synthetic is less aditives (sometimes no additives) are used in multi vis oil.
My work has always involved machinery reliability, lubrication is a big part so I've had quite a bit of training in that area. One thing I've learned is when choosing a multi vis oil, it is better to opt for a narrow range because if it stays in your engine long enough for the additive package to wear out, your viscosity begins to slip to the lower number. There are always exceptions. I use Mobil One 10-30 in my jeep, and I live in a warm climate. Main reason I use it is to extend oil change intervals.
I was at a class about 5 years ago on refinery lubrication, the guy giving the class services the now Valero refinery in Port Arthur, TX. That refinery has excellent machinery reliability. This guy favored Chevron lubes, he used DELO 15-40 diesel oil in his gasoline Ford pickup. His opinion on the difference in gas mileage than a lighter oil, if he passed one car it would negate the savings on that tank full. Chevron was famous at the time for long MTBF (Mean Time Before Failure) runs of their equipment. Some of their stuff was running more than 60 months 24/7 while the industry average was closer to 24 months, Chevron was quietly making some of the best lubes on the planet at that time.
He got into the latest (at the time) progress in mineral oil. Older oils had a lot of wax and paraffin, engines used to gunk up more. Paraffin were removed by separation but in the late 90's lube plants started using hydro cracking and hydro treating to crack the paraffin molecules into lube molecules. Oils refined by this method are call "group 2" oil. Interesting that at that time Pennzoil was a group 2 but Castrol was still a group 1, I’m guessing they are all group 2 by now, really closed the gap between mineral and synthetic oils.
He mentioned that the worst oil filter you can buy is a Fram, and the ones sold by Walmart are the worst Frams. Oil filters he recommended are Purolator Pure One, Wix, NAPA Gold and Mobil One. I've been using NAPA Gold since there is a NAPA right up the street.