Synthetic oil
 

Has anyone heard anything about synthetic oil dramaticly increasing MPG?

I want to try in but want to hear what you all have to say first.

I've seen some big numbers on dyno tests in the enthusists magazines. Personally going from mineral based to synthetic of same viscosity showed little improvement. Going from 10w-30 synthetic to 5w-20 synthetic was too small to measure accuratly. At operating temp oil pressure took a huge dip.

If synthetic dramatically increased MPG, then manufacturers would require this type of oil so they could boost their EPA fuel economy figures.

Changing to a synthetic oil of the same viscosity won't make a difference. The benefit of using synthetics is a longer life without viscosity breakdown, as synthetics (and the very refined mineral base stocks sold by many manufacturers as synthetics) naturally have a wider viscosity range than typical mineral oil and require fewer friction modifiers, which break down over time.

So, how about changing from 5W30 mineral to 0W30 synthetic?

the only thing that will show 'dramatic' increase in mpg is "adjusting the nut behind the wheel"

Changing from 10w30 to 0w30 isn't likely to net any noticeable mileage benefit. The only difference in the two weights is the cold start viscosity. One acts as a 10 weight on start up, the other acts as a 0 weight on cold start up and they both act as 30 weight on a fully warm engine. I've never used synthetic, but if mileage gain is all you're looking for in the change from conventional to synthetic it wouldn't be worth the extra cost associated with synthetic. I think the money would be better spent on giving your car a tune up. Personally I've never had any problems with conventional oil in about 1M miles of driving, with one of my cars being at 518,700 miles on the original engine. I run 10w40 in my '88 Escort and have a lifetime average since I started my gas log on this site of just over 41.5 MPG combined. The old highway EPA rating on it is 42 and the old combined rating is 37. Adjusting driving habits will do much more for fuel efficiency than changing to another weight oil.

I agree with mcrews, with the exception of modification on the level of the Aero Civic.

no credible reason to not use "synthectic" oil
 

mwebb look at my fuel log, no diffrence at all