Octane

If you mean it runs smoother with HO then you need a tune up, if you just like more power than ok, but HO doesnt increase milage anywhere near enough to offset its extra cost.

Some high-performance cars do get better mileage on "HO" gas. My Civic EX gets 10% better mileage on midgrade, which is more than enough to offset the price difference. I'd suggest to the original poster that he try midgrade. And to answer his question: stale gas has a distinct odor, kind of like kerosene. You'll know it if you smell it.

All cars get a bit better milage with HO, my v40 gets maybe .10 - a tenth mpg better, but that hardly equals the 10% plus price difference, I go from 22.3 - 22.4 to 22.5 on HO on a same loop driving. I would have to get near 25 mpg for the price difference to may it a break even payback.

I would be very surprised if your car ran much better on 93 octane than on 91, 89 or 87. If this is true then the knock sensor might be dead on your car.

I understand that with a well tuned car one can eke out a small net cost benefit by switching to lower octane gas. The difference is not simply the difference in price per gallon however.

I doubt that you are the only person buying high octane gas.

Just continue to buy at busy stations. I've driven cars for over 45 years and have yet to buy a tank of bad gasoline.

Yes, you could do that. You should plug all the variables impacting the net cost of gasoline to you as a consumer into a spreadsheet and see what the real difference is.

My owner's manual calls for 91 octane. I don't know how much it would help my car if I used 89. I can not hear engine knocks with 89 but that doesn't mean they aren't happening. And I can't think that constantly retarding the spark of the engine is healthy.

At this point I will stick with 93 and keep a sharp nose on the odor.

OUS

I would be very surprised if your car ran much better on 93 octane than on 91, 89 or 87. If this is true then the knock sensor might be dead on your car.

I have no idea how well it runs on 91 octane, I have not seen it available in my area. But on the 93 octane that is available, it runs much better than on 89 or 87.

I understand that with a well tuned car one can eke out a small net cost benefit by switching to lower octane gas. The difference is not simply the difference in price per gallon however.

I doubt that you are the only person buying high octane gas.

Just continue to buy at busy stations. I've driven cars for over 45 years and have yet to buy a tank of bad gasoline.

I did buy bad gas at a Valero station when prices shot up last year. I was able to recognise the problem before damage was done to my wife's Saturn. It turns out that the propriator of the station was adding water to the underground tanks to streach his supply. He is not in business now.

Yes, you could do that. You should plug all the variables impacting the net cost of gasoline to you as a consumer into a spreadsheet and see what the real difference is.

I am more concerned with the health of my car than the price of fuel at least at this point. I'll stick with buying premium.

Lower octane will probably not hurt anything, there's a pretty significant safety margin, but I would stick with what the manufacture recommends. If the car was designed to take advantage of high octane fuel then I don't see much reason to skimp, even at the peak of high gas prices, it was only a few dollars more per tank than the low grade stuff, yet a lot of people blow the money they saved in gas on a single latte on the way to work.

Generally gas stations will order less of a grade that isn't moving as quickly so they don't get stuck with stale fuel. So long as you buy from a reputable station you shouldn't have a problem.

No, not all cars get better mileage on HO - it depends on their design and the driving conditions. Our '95 Camry gets better mileage on regular, as long as there aren't a lot of hills involved. So did my old Civic.

It should also be noted that "Midgrade" isn't a separate gasoline. It's actually a pump-blended mixture of Regular and Super, so as long as people are buying Midgrade, the Super is getting used up.

I didn't think this was a 240? If it was, then plain old 87 octane would be fine. The only 240s that require premium are the turbo models.

You're right - it's an 850 turbo. I was confusing the thread with the one about the B200 engine. I still think that Midgrade would suffice for normal driving, though.

I did not know that! This knowledge only makes me more suspicious of midgrade.

I'm sticking with 93.

OUS

Yes, mid grade should be fine, it's a good compromise.

On a 240 Turbo I would recommend premium though, especially if you have turned up the boost beyond stock. Those have no knock sensor so your ears are the last line of defense.

There has been no level ground here since the last ice age. And no sissy Acura dares challenge my '95 850 turbo wagon. :>)

OUS

Why be suspicious? If you mix something containing more octane with something containing less octane, you will get something in the middle.

Sticking with 93 certainly won't hurt anything though, it sounds like the peace of mind will be worth a few extra dollars to you.

A well maintained 240 might could take my lumber wagon if the wagon was fully loaded. The driver rarely is.

OUS

You could also mix it with 87 and nothing. Selling it at the 89 price.

Still gonna stick to the 93, I think.

OUS

FWIW, using HO gasoline provides me with better mileage, but only on the highway, about 10% better or slightly more. In the city, I barely see any difference, Of course, I see a difference when I accelerate in city/highway.

Cars used for tests were all non-turbo and 240s and a 740 and S90/960.

My 2 cents.