Have 3 grades here—87 octane, 89 octane and 93 octane.
Always exactly 10 cents difference between all 3.
My car is supposed to run on regular=87. Doesn’t really like it. Pings on acceleration. 89 is OK but don’t like spending and extra 10 cents a gallon for an extra lousy 2 octane. Usually I mix half and half 87 and 89 and that works pretty well without costing so much.
A couple or 3 questions—
1----Why, when my car is supposed to run on regular (87), does it ping and knock? Car is 20 years old. 83 Buick Regal with 4.1 V6. Does age have something to do with it?
2–Why is there a 10 cent difference in price between each of the 3 grades? Do they use the same gasoline and just use an additive when filling the gas station tanks to increase the octane? Or do they actually have to carry 3 separate reservoirs on those big gas tankers?----(if so I can understand a big price difference)
3–Why is there a 10 cent increase from 87 to 89 (2 points more) and a same 10 cent increase from 89 to 93 (4 points more)?
Been considering mixing 93 octane and 87 octane at some ratio or other to take advantage of that strange disparity in pricing.
The reason why your car is pinging is because you have carbon build-up in the combustion chambers: the carbon takes up space otherwise used by fuel/air mixture ultimately meaning that you end up with a higher compression ratio requiring higher octane fuel.
Furthermore, the carbon ends up getting incandecent at operating temperature, furthering pinging and knocking.
A neat trick to fix this is to drive around until the engine heats up and fill a spray bottle full of water to spray down the carburetor.
The fine droplets scour the carbon off the combustion chamber.
Because of carbon build-up in the combustion chamber and/or improper working of the EGR (exhaust gas recirculation) system. I’m sure it didn’t ping when new. A carbon cleaning procedure (“Motor-Vac” is the best known one) could be very helpful. A competent garage should be able to evalutate whether the EGR system needs attention.
Well, disponibilite, I can give you some of the information you seek.
If your car was designed to run on 87 octane, and it pings and knocks, there’s 2 answers. First, you may be getting substandard gasoline; have you tried a tankful from another dealer? Second, your car needs a little work. Tell your mechanic about it, and she may be able to nudge the timing a bit, or replace the cracked vacuum hose that runs to your distributor.
2)I don’t know how they give you three grades of fuel. I’m reasonably sure it has nothing to do with 1920’s style fuel rays.
3)I really tried to answer your questions about gasoline prices, but I kept collapsing in helpless laughter. Perhaps somebody can explain (with a straight face) how market pressures, world oil prices, and fears in the mideast can drive pricing strategy. I can’t do it. There ain’t enough Botox in Indiana.
I was just wondering about that 10 cent differential, not gas prices in general.
I can understand a huge differential (seems huge to me anyway) if gas tankers actually had to carry 3 separate tanks for the different octane blends.
If all they do is add an additive to the same gasoline to increase octane when filling tanks at a gas station----------then 10 cents increase per grade seems like a huge ripoff.
Enola–
I have heard about that water spray trick. Have always been a little afraid to try it. Have heard if you overdo it just a little you can blow the engine.
Yes, the pinging is caused by carbon buildup. You can go to your GM dealership and ask for a bottle of “GM Top-End Cleaner”, and follow the directions on the bottle. It’s about $5 and does a great job. Just be sure to do this in a remote parking lot as it (Temporalily) causes huge amounts of smoke out the tailpipe.
If you’re not comfortable doing the de-carbonizing yourself any competent shop can do it. You’ll also be rewarded with an engine that runs much better/smoother.
As for how gasoline octane works, there are 2 grades coming out of the refinery. 87 octane and (in your area) 93. Both have to be trucked to the gas station, and are stored in separate underground tanks. To get 89 octane the two base grades are mixed in the pump at a certain ratio.
Yes, you can mix it yourself and save a few cents.
The reason for the price difference is mostly based on volume. Since most of the gas sold is 87 octane it is slightly cheaper. Law of volumes. Of course 93 octane also requires more of the octane enhancing additives which cost more than base gasoline.
I agree with the carbon build up part, also the timing can be off, but I wouldn’t recommend spraying water in the intake of a running engine. Water doesn’t compress and something will have to give, probably a rod.
Obviously one does not pour copious volumes of liquid into the engine for fear of what you mention. However, what was described is an old technique that will not cause harm if the water is entered judiciously, for example from a spray bottle as suggested. There is room in the combustion chamber for small amounts of non-compressibles.