Consensus on 87 Octane in a Turbo

KEWROCK · Post by **KEWROCK** » 26 Oct 2010, 15:02

Is there a general consensus on running a turbo on regular?

What's the deal, am I going to eventually burn a valve or not? I've read post after post with no conclusions. I'm not concerned with MPG's or increased performance. I've come to the conclusion that in my car it makes no difference. I get no additional fuel economy, and performance enhancement is negligible, if any.

What worries me is that I keep reading unsubstantiated claims of BURNED exhaust valves. Now I can understand if it were WORN valves due to preignition valve rattle from gas not burning fast enough. But my Volvo runs smooth and quiet on even the cheapest no-name fuels. Unlike my super-charged T-Bird, that car COULD NOT run on anything but premium. The valves sounded like they would literally shoot out from under the hood. It still didn't run hot, just too noisy for prolonged use.

Now I'm not a auto mechanic, but I've worked on small air-cooled engines my whole life(tractors, generators, chain saws, mowers, etc). The last thing you want to use in any air-cooled engine is premium. It burns way too hot, leading to scorched, melted pistons, warped heads, and most commonly burned exhaust valves. Putting premium fuel in a small chain saw will kill it before you can use up the half pint fuel tank.

So why should a cooler burning fuel burn an exhaust valve?

Post by **tjts1** » 26 Oct 2010, 15:58

If 87 octane works, keep using it on your turbo. The only time you really need the octane is under boost at high ambient air temp (aka flooring it in the summer). These cars have a relatively advanced engine management system with a closed loop knock sensor that advances timing right up to the verge of detonation, regardless of octane. The 99% of the time when you're not gunning it and don't need peak power, your fuel economy will stay the same. Use 91 if you need max power in the summer like driving in the mountains maybe.
I have a non turbo that has non 208k miles so far on 87 octane. Its different, i know, i know.

I didn't know chain saw motors didn't like premium. I learn new things every day.

Post by **boosted5cyl** » 26 Oct 2010, 16:57

Higher octane fuels burn longer, not hotter. It would be really weird to say the least to have an engine run hotter on higher octane fuel, all other things being equal in its content.

Octanebooster · Post by **Octanebooster** » 27 Oct 2010, 16:40

Hello Volvoians,
My personal experience is ( for turbo ) run the highest octane you can find. Not afford,but FIND !

Why ! ? because if um not mistaken, it was on this site that for turbo Volvos if you don't run 93 octane it will lead to
head gasket failure ! Which i believe happened to me. All fixed now but I' ve run 93 ever-since.
As for the idea of only use 93 if you demand max power ! ! ! Do we demand that all the time ! ?
Few bucks more, i think it's worth it !

I have a 96 turbo with over 160k
Ported and Polished, both intake and exhaust,I mean i opened those 2 up ! cuz i had to do the head gasket.
It totally runs mad, with the modifications ( P & P ) I've done !
Never dreamed, it would improve the performance, way it did !
One other interesting notes about these mods.
I tested the O2 sensors before doing these mods. After the car was back together and running again,
I tested the O2 sensors again, and the mods seem to have " opened up " the parameters or the range limits
of theses sensors....like it gave them, " new life ! " Because before they were close to the ends of their limits.
Now there is plenty of " room " . Like the limits are something like MIn. of .100 to say .900 ( mv or whatever )
now they are well within the range, like .300 to say .800 range !

Thanks for your time and thoughts on this post !

Octanebooster

Post by **jblackburn** » 27 Oct 2010, 17:52

I always run at least 89 - and usually 93 during the summer - my turbo is WAY too slow to boost up running 87 and it annoys me. You can actually feel it being held back as opposed to running on mid-grade or premium. I have no idea whether or not it leads to burned valves - the engine definitely retards timing, which should correct/keep that from happening.

3wagons · Post by **3wagons** » 27 Oct 2010, 19:18

Maybe I'm ignoring bigger maintenance issues with my XC70, but when I run 87 or 89 I get the check engine light after a couple of weeks. If I use 91 or higher, light goes out after about a week. Tried this numerous times. Haven't noticed a difference in economy or performance though. Been using premium since this spring & haven't had the dreaded CEL back. Only a couple of extra bucks each week. Nothin's too good for my baby.

Octanebooster · Post by **Octanebooster** » 27 Oct 2010, 21:29

Hello Volvoians,
Interesting comments here. Thanks. We have some thinkers and tinkers here.
When i took the top-end off on my 96 850 turbo with over 155,000 on it, I was amazed at the condition of the
pistons and valves. They looked like they could go another 200k. NO exaggeration here folks. I measured pistons
and cylinders for wear, " by the book " and found everything well within limits ! I was amazed.
Now that i think of it ! !! LOL Not really sure how the " lower " octane affects the head gasket issue ! !! but but but !
Yeah, it definetly runs better with the ported and polished intake and exhaust ! Actually, the manner in which i ported
the intake, left it " ruff'nuff ", to keep the airflow turbulent enough, to benefit the air/fuel mixture. The exhaust however
is a much different story. That is where i spent the extra time getting it really smooth. The exhaust was truly shinny smooth
when i was done. The reasoning behind that was, get it out fast, no faster, ok way faster than the sweds had time for !

Octanebooster says get the facts and get out the exhaust.

Post by **Ozark Lee** » 27 Oct 2010, 22:58

Is there a general consensus on running a turbo on regular?

Regular in a turbo will burn the exhaust valves over time.

I am commuting 100 miles/day on the interstate on fairly flat land with the cruise control - nothing radical - and I have been running 91 mid grade to save the extra dime/gallon but I am not going to go to the 89 octane.

My turbos love the 93 octane but I don't think the '91 is hurting them.

There is a local tire shop that has a pump where they sold 100 octane racing fuel and I was really tempted (even at over $5.00/Gallon) for a Bonsai run to the cabin but they shut the pump down about a year ago so I couldn't try it.

...Lee

Octanebooster · Post by **Octanebooster** » 28 Oct 2010, 10:21

Hello Ozzy,
Yeah,too funny ! The 100 octane stuff ! I work on aircraft ( Cessna 412 Ultraliners ) in the early 80's and used their fuel
in my car all the time...WOW ! Now, i just add the octane booster that is available at parts store ! It definitely makes a
difference !

Post by **boosted5cyl** » 28 Oct 2010, 13:45

Just be sure the higher octane is unleaded. Leaded will kill your cat and O2's. That said, its unlikely to make a difference. Yes ECU's adapt by using knock sensors, but only within certain parameters. 100RON is generally outsite these paramaters in a stock ECU. Again, higher octance fuel doesnt have more uumph, in fact it has less. The higher octance means its less succeptable to detonation and its flame propegation is slower. As a result you can use forced induction, more agressive ignition timing and higher compression ratios to produce more power. By itself, higher octane fuel offers no power advantage, zero, zilch, nada.