2010 Mini Cooper Mileage

I have a 2010 Mini Cooper (base model) that I got new during the summer. When I use regular gas instead of premium I get better mileage (up 3-4/ga city and 7-8 hwy). How is that possible? Am I doing any real damage to the car putting regular in instead of premium?

As said in many other posts on the reg/prem debate. Use what the owners manual specifies. If the manual says prem. required you may end up with serious engine damage for saving a couple bucks per tankful.

I’d be willing to bet that the driving conditions and type of driving had more to do with the difference in fuel mileage here. Also if IIRC the Mini is a car that requires premium fuel. If you value your warranty use 91 octane or better.

Read your owners manual.
It will tell you what the pitfalls of using regular gas are in your car.

Anyway, your car has a knock sensor.
When you use low octane gasoline, the car alters the ignition timing in order to prevent detonation. This reduces engine power, and, possibly, can increase engine deposits in the combustion chamber.

If your car suffered a mechanical failure, and the dealership asks you what fuel you use, if you say anything other than high octane, they can (and sometimes will) deny the warranty repair claim.


I do not recommend using anything other than premium gasoline in your Mini, regardless of your claimed mileage increase.

I think something besides the fuel switch is causing the difference. 7-8 mpg increase in highway mileage is HUGE, and hard to account for. Whatever is causing it, I doubt it’s the fuel.

You are causing harm to the engine of your car by using regular gas, and you’re not saving enough money to justify it.

Why did you buy a premium brand car if you weren’t willing to buy the premium gasoline it requires?

BMWs, and the Mini is a BMW, require premium. That’s just a fact of life.

It’s your car. Do what you want, but I think it’s a shame to damage an engine just to save a few pennies.

If there is NO engine rattle and the spark plugs are burning normally then you’re unlikely to suffer any engine damage. However (there’s always a big however) if the engine did suffer any damage (summer heat, pulling mountain grades, chronic hard acceleration, etc. is worse) then an engine teardown would likely reveal the regular gas as being the reason and your warranty would be DOA.

The part I don’t get is how going from Premium down to Regular would improve mileage at all, much less by that much.
Premium Ethanol based and the Regular is not???

I wonder if maybe the regular vs premium difference might have been a winter gas and/or ethanol.

There is no reason you should get better mileage with regular, and there is no reason you should get better mileage using premium unless your car is designed to take advantage of it. Regular vs premium does not have more or less energy in it nor is it in some way a “better” fuel it is just a different fuel. Sort of like blue vs red cars. One is not "better than the other.

Please, Let Me Add Some Friendly Advice To The Vehicle Owner.

This is a case again where We should be asking you the question, " Am I doing any real damage to the car putting regular in instead of premium?"

You’re the one with the Owner’s Manual. Others have already suggested that you read it to find the answer to your question. I strongly recommend that you read the manual from cover to cover. It doesn’t have to be read in one sitting, but you should read it, soon.

I’ll bet you will learn about some features of your car that you are not fully aware of at this time and I’m pretty sure that if you follow the requirements and recommendations in there that the car will provide better service to you.

Many people who pop on this site because they are having car problems (some of them catastrophic ones) could have avoided the problems simply by reading and adhering to instructions in their manual. Look carefully at the maintenance schedule, too.

Regarding your query, which we’ve had here many times, “Premium Fuel Recommended” means that you will probably cause no damage with regular grade gasoline (but performance will suffer). “Premium Fuel Required” means that you can cause engine damage using regular fuel. Also, there is usually a sticker at the fuel fill location with this verbage.

How is it possible that MPGs are up with regular ? I’m with Joseph on this and will say that it doesn’t add up unless it’s an issue with summer blend vs. winter blend gasoline.

Good Motoring,

High octane = slow burn rate. The cars that require premium were designed to be most efficient / make more power based on the slow burn rate of premium. longer stronger boom on top of piston instead of small firecracker pop with reg. Make sense? Your mileage may be better with reg is driven very sensibly as long as not under load and having to retard timing for spark knock. I’m not a technician what do I know?