86-Pace-Car

Hi all, I just bought my '86 last week. Haven't filled it up for the first time yet. The previous owner said I should fill up with Premium, the highest octane I can find. The best I can do in these parts is 91. Do you think it's a good idea to use an octane booster or is that even necessary? Thanks in advance!

antfarmer2

Wast of money imho

vader86

Not even necessary. Your engine has low compression, even with the aluminum heads.

My 86 got by just fine with no knock on 87 octane. You always run the lowest octane that allows you to prevent knock.

Cruisinfanatic

you don't even need any more than 87 let along booster.

c4cruiser

91 Octane premium is pretty common across the country and it will work fine and there is no need to use an octane booster.

You can also try a mid-grade of 89 octane to see how that works. 87 octane regular works too but you may hear some pinging under heavy acceleration or going up steep hills. In normal driving around town, 87 will work with no problems.

WW7

I only run 91 octane in my 383, and it has 10.25 to 1 compression ,so you don't even need the 91 octane....Run what the owners manual says and you can't go wrong...WW

volkswagens-for-life

It's to my understanding that bottles of octane booster dont boost your octane worth ANYTHING... I've heard less than ONE octane percentage? Maybe I'm wrong.

DGXR

I think the L98 was designed to run 87 octane...? Correct me if wrong.

I was told that when they say the product "increases octane 3 points" they mean three tenths (0.3) not three full numbers. Waste of money.

I use Lucas fuel treatment ($27/gallon on Amazon which works out to just over $1 per tank), not for its octane-boosting properties, although the label does say "eliminates the need for higher octane fuel." Food for thought OP.

c4cruiser

Premium fuel was the recommended gas to use. It will state that on the trim piece around the gas cap. The owner's manual does state that the engine was designed to use premium, but the ECM will compensate for using lower octane gas. Some reduction in acceleration performance will be noticed using a lower octane gas.

DGXR

Huh. I always thought the 1985-1986 L98 compression ratio was 9.0:1, which is relatively low compression and should run great on regular. In 1987, the L98 compression ratio went to 9.5:1.

My 2006 Tacoma 4-cylinder has 9.5:1 compression and is recommended to run 87 octane regular. Maybe the aluminum head/block and advanced electronics are why it can run so well on regular?

Cruisinfanatic

wrong. OM says 87 octane for an 86

Benny42

I will only put premium in my '86 on my way to the track. I don't know if it helps there
but it can't hurt. All other fill-ups are regular. Post up a picture of it

gerardvg

Hi

You can run low octane, the ecm will respond to low grade fuel when it gets a knock (pinging) signal. It will retard the ignition to compensate, so yes you can run regular unleaded. It will not make a difference filling with high octane unless you reset the ecm, so it can relearn and take advantage of the high octane fuel and run more advanced ignition.

I found even when stock standard my 85 would ping with low octane, i never have that problem with high octane.

Disconnect the ecm wire and reconnect when you have premium high octane fuel, the ecm will then run more advanced timing and you can feel the difference. Especially when you accidently put low octane in and she pings like crazy till the ecm retards the ignition to compensate.

For anyone not interested in performance low octane is fine, but those of us that have gone from high octane to regular know that pinging sound.

I now have been running a blower for the last 10+ years and only run high octane, its a small price to pay for the good stuff.

WW7

This is what my 89 manual says....WW

QCVette

My '85 OM says 87 octane but as low as 85 can be used.
My '87 OM says premium but 87 can be used but reduced acceleration.

I wonder if the change between them happened in mid '86 when the aluminum heads began?

DGXR

The 1985-1986 L98 has a compression ratio of 9.0:1.
In 1987, the L98 compression ratio went up 0.5 (from 9.0 to 9.5:1).
That's why premium is "recommended" for the 1987.

For normal driving with occasional spirited runs, 89 octane should be plenty for the 1986 L98.

vader86

Running premium when the engine does not need it is wasting money, and lowering your MPG. It takes more energy to ignite a higher octane fuel, that is the point of octane.

An 86 L98 with stock compression and OEM chip tuning will not be able to properly use premium fuel under any circumstances. I know, I've tested and scanned to find out. An 88 does not even need premium, mine would never knock on 89 octane when it was stock.

Paul Workman

Could be, methinks, at lest according to my "Corvette Tech Data" wall poster: the 86 MY had both 9.0 and the later 9.5 compression heads...for what it's worth.

It was in the mid/late 80s when the EPA required ALL cars be able to run on 87 octane, including the LT5 with its 11.0 compression. This was made possible with the use of computers and knock sensors - the key to the performance potential to come.

Tom400CFI

Combustion chamber technology and (electronic) engine control advancements are why modern engines like your Toyota (and all others) can run higher compressions on the same fuels.

Tom400CFI

Also a waste of money.