My wife is thrifty and always puts the cheapest grade of gas in our car. I say that you must put at least what the manufacturer of the car suggest. If a car requires only the lowest grade of gas and you put in something higher you have wasted your money…HOWEVER if your car specifically says it needs 91 or higher and you put in something less continuously you can harm your car…am I correct
Using a lower grade fuel where a higher one is required causes the knock sensor to compensate for the difference and the engine will have less power.
Your post is correct.
depends upon whether it (manual) says “recommended” or “required”. If the former, using lower octane gas will cause loss of power and lower milage (whether or not it’s noticable depends on the car). Using lower octane than “required” can cause damage.
Your wife is too thrifty. The cheapskate pays the most when damage occurs.
You are correct, your wife is wrong, and your gas mileage is undoubtedly lower than it would be with the correct fuel octane. In some cases, engine damage can result. Tell her that you cannot afford to save money that way.
Normally I would you ignor the facts and let your wife think she is right while you know you are. However in this case it could (assuming the owner’s manual says it “requires” premium casue some damage in the long run. So tell her, but be nice about it. On the other hand if it just recommends premium, I would keep my mouth shut. You will know you are doing something nice for her and it is not going to do any damage. You both can win that one.