page@ucla-cs.UUCP (03/04/85)
My new (1984) Subaru GL wagon asks (in its manual) that it be given gas of no less than 90 octane or "serious engine damage may result". Before reading this part of the manual, I had bought a tank or two of unleaded (87 octane) and the car ran ok (pinging only on hard acceleration). Since then I have bought premium unleaded (92 or 93 octane) and sometimes the unleaded from Union 76 which is 89. Question. What will happen to my car if I switch back to unleaded ($1.07/gal.) instead of super ($1.27)? Also, is 89 octane ($1.18) close enough to 90 not to matter?
notes@isucs1.UUCP (03/17/85)
That "ping ping" you here is called detonation. If it continues for very
long, it will blow the ring lands right off your pistons. There are several
ways to prevent this. First, you could take it to a qualified auto mech and
have him retard the timing. Second, you could start paying for the kind of
gas the engine needs. Or, you could lower the compression ratio in your en-
gine. This can be done by changing the pisons (if you can find them) to those
that give you less compression, or, I have heard that putting two head gaskets
on each head will lower the compression ratio. I have never tried this but
I suppose it would work.
There is also water/methenol injection, the water is vaporized into the
the air/fule mixture where it raises the flash point thus preventing deton-
ation.
Drew