85 Octane Fuel

Can these little cars run on an 85 octane fuel or is it best to keep them on ay least an 87 octane? I'm only asking because I passed a gas station on my way home from work and saw that they offered 85 octane which is about 30 cents cheaper than the 87.So if it is possible for them to run on such a low octane I may start to use it to save even more money on gas. And so that I can laugh at all of the fools filling up their big rigs.

Only way to know for sure is to try it. Most Metros came with timing set to 5 before to keep NOX emmissions down. This is quite late and the engine will give more power and better mileage set at 10 or so, you just have to retard it for your emissions test. If you haven't advanced it (and you car is not one of those that came from the factory with 10) that 85 octane will probably work fine. Just listen for ping, a hollow, rattling sound usually experienced at two thirds throttle or so. As long as it doesn't ping, you're fine. Remember that the first tank will be mixed with a little of the old gas, so it will be a couple of tanks before you have pure 85 in there. Ping also may show up later as weather conditions change or the motor wears or collects carbon deposits, so keep listening.

and listen for the sound of ratteling marbles. that is an indication of low octain affecting the engines timing and pre-detination.
you will know within two tanks of fuel.

I'd double check to make sure it wasn't E-85. I've seen gas stations here that say 85 octane and when you get to the pump it's actually Ethanol.

So is ethanol 85 octane different from 85 octane? And does one need a timing light to check on the timing set?

What altitude is the gas station at? Generally 85 octane fuel is only available at high altitude locations. At anything over 4000' or so 85 octane should work fine. Down at sea level it'll ping.

Q

The gas station is at about 2500' above sea level.

85 octane is the lowest we get here at 5,300 ft, and that's what my Geo has been running on since I bought it 30k mi./5 years ago.

The highest octane you see around here is 91 (Super), unlike the east coast, where I often saw Super with 93 or 94.

Passed by the gas station on my way home from work and saw that it was ethanol 85. Which people have said won't work in my engine.