would the better gas mileage offset the cost of Premium? I’m getting around 27-30MPG’s right now, I have a 1983 Mercedes 380. It has a 3.8L V8.
How much better gas mileage would I get in my Mercedes if I used Premium Gasoline, and not regular?
Posted by admin on June 21st, 2010
Posted in Used Mercedes 
It will actually impair your performance and mileage A lot of your mileage will depend on driving habits instead since you are getting that kind of mileage I would say you do quite a bit of hwy miles in that car and the only way to do better is to keep it in perfect tune as well as having a extremely light touch when accelerating also taking it easy so you don’t slow for traffic as much .
unless your car is made for premium fuel, (supercharger, turbocharger, high compression, advanced timing) then it will not help performance..
No better. Higher octane won’t give you better gas mileage.
Octane ratings are necessary to prevent detonation (pinging) under loads. Some cars, probably not yours, have knock sensors that retard timing to allow lower octane gas but at the price of reduced power.
Is your engine high compression??? Does your owner’s manual call for premium fuel?? Is there a decal in your fuel flap that says," use premium only"??? Then you should be using premium!!! Most German engines have a knock sensor that retards the timing if it senses a knock. This prevents engine damage and may cost you power and economy, if you’ve been using regular. If your engine doesn’t require premium, then it’s a waste of money to use it. If it calls for premium and you haven’t been using it, then you probably will get a little better gas mileage, but not for a couple of tankfuls, because the ECU will try to re-learn your driving habits and adjust the engine parameters accordingly.
As some of the others said, unless your manaul says to use it, then it is not worth the price. Making sure your tires are inflated properly, you don’t play “footsie” with the gass pedal while driving, along with proper maintenance makes more difference in mileage than the type of gas.