In article <D6cqd.7794$Mu3.802926@twister.southeast.rr.com> ,
"K-town" <jdu52580@carolina.stopspam.rr.com> wrote:

> Not being an engine expert, I figured I'd throw this question out to
> this NG. I have a 1990 Civic LX, 1.5L DPFI 5-speed, and usually I put
> regular unleaded (87 octane) in it. Every once in awhile I'll put mid-grade
> (89 octane) or premium (92 or 93 octane) in it because I heard that doing so
> will keep your injectors clean. (Is that true?)

Prior to 1995, it may have been truer than not.

The oil companies used to put detergents into only their higher octane
fuels, as an incentive to get you to pay the price.

Around 1995, though, the feds defined a minimum level of detergency to
be put into ALL fuels. This dried up the oil companies' ability to
claim that "buy our expensive stuff, and your car will be cleaner and
run better".

Shell is back into that game now, though, with their V-Power. They
simply add MORE detergents to their 92 octane gas than is specified by
law.

This all being said, you can add a can of Chevron Techron to your fuel
every now and then and get the same results or better. And it's MUCH
cheaper than using Shell V-Power on an ongoing basis.



> Once I really splurged and
> put 100 octane fuel in it (only 5 gallons) and it did run pretty good.

Not as good as you think. You wasted your money, AND you wasted fuel on
top of that.



> One
> thing I noticed, is that if I run premium (93) in it several tanks in a row,
> it will actually not run quite as good. It's a very minuscule difference,
> but I can tell there is a slight decrease in performance.

That's right. The higher octane fuel won't give your engine as much
power as the lower octane fuel, believe it or not.

http://www.faqs.org/faqs/autos/gasoline-faq/part1/