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jaiman · 08-14-2003, 03:26 PM

I was reading some posts earlier talking about fuel grade. I have been running regular in my mh. Seems to work fine. NO knocks or pings. Got me thinking about whether the extra expense of mid grade might help boost power when travelling through the mountains. Does anyone have a comment on this.

Jai

54FlyingCloud · 08-14-2003, 03:54 PM

Pull my '54 22 footer with a F150 5L 3.55. When I pull with regular gas in tank may get a little ping on an uphill pull. Put in midgrade and made a very noticeable difference in pulling up hills. Just got back from trip in Rockies where I experimented with premium and could not notice any difference compared with midgrade. For me, using midgrade was definitely a positive for power increase and no knocking or pinging.

wb13798 · 08-14-2003, 05:45 PM

i switched to mid grade i dont get as much valve ping and it seems to pull the hills better. lol
al

59toaster · 08-14-2003, 05:57 PM

454 has under 8:1 compression. Should do ok on Regular. I run my 454 burb on it and not had any problems. My burb is FI with a knock sensor so that helps. I have not noticed a difference in performance between the two. Just for a laugh I need to tank up tomorrow and I'll run mid and pay close attention to how it performs.

wb13798 · 08-15-2003, 08:38 AM

toaster that wont be a good test for a 454 set up with no knock sensors. you probably wont notice any difference.. lol
al

will · 08-16-2003, 08:48 AM

I started out using reg. gas my first season with the 89 345le,but switched to mid grade because of the rumers I've heard about the engine burning pistons. Right away I found that I get better mileage and there is no "run on" when I turn the engine off.

ALANSD · 08-16-2003, 11:40 AM

I have been using mid grade for two years, and after reading this I guess i will continue to, its too bad its up to 1.60 gallon here, but the extra .10 is worth it. I am still getting 8-9 mpg, running roof air and towing my Saturn, so I feel pretty good about it.

PeterH-350LE · 08-16-2003, 01:29 PM

No low octane for me.

jaiman · 09-01-2003, 03:54 PM

Well the my personal results are in. The mid grade gas was well worth the $2.09. I had plenty of power going up and over mount Hood. the side benifits were better mileage, and lower engine temps. (cant figure the temp thing other than the engine didnt work as hard.) Now to go and post in the repair forum. Got to replace the leaky gates in my waste system. Yuck.

Silvertwinky · 09-29-2003, 12:28 PM

I tow with a Dodge Ram 3500 8.0 V-10. The owners manual says "Use only unleaded gasoline having a minimum posted octane of 87."

Can it be harmful to use a higher octane than it calls for, or is it saying that is the minimum to use?

I've found in the past when I had the g-20 van that using a higher octane really helped with the power.

I've mixed it in the past and I can't say that I can tell a lot of difference it may increase the MPG somewhat. Does it help keep the engine clean, etc...?

Thanks,

Silvertwinkie · 09-29-2003, 01:08 PM

My Chevy 350 calls for plain old 87 too, however, my observations/perceptions was that using the 93 octane did have better throttle response and power.....

Now, I have my powertrain control module programmed for performance so 93 octane is now required in my car. I was in a pinch once and a rural place only had 87 octance. I took on a few gallons so that I knew I would not be out pushing and the engine, once the fuel made it through the lines caused engine knock. Back to 93 and all was well and happy again.

Eric

garry · 09-29-2003, 03:54 PM

I also have the GM 350. I use 93 octane when towing. Makes a 2 mpg increase and better pulling power.
When pulling my bass boat or just regular driving I still use the lower grade fuel.

Garry

John · 09-29-2003, 04:08 PM

While towing I run mid-grade in my 5.3L 4:10 Silverado.

Regular when I'm running around town.

$1.46

Silvertwinkie · 09-29-2003, 05:44 PM

Garry,

I can tell you first hand that by getting your '96 a new air/fuel mixture program, you'll get about 10HP and a few Ft/Lbs of torque....then again you'd have to run 93 straight all the time and at $2/gal now....then again, few buy these thirsty beasts hoping for 30MPG!

Check out pcmforlessl.com. Bryan is a VERY straight shooting guy. You will be satisfied with his work.

Eric

garry · 09-29-2003, 06:03 PM

Hmm....Good tip however, with 163,890 miles on the 1996 Vortec 350V8 with 324 GR it has just about seen it's day. 17/19 mpg on the road no tow, and 10/12 mpg towing depending on wind, speed ect.

Garry

Silvertwinkie · 09-29-2003, 06:07 PM

Garry,

I see your point!

Nearly fell out of my chair after readin it.

Guess you got you your money's worth out of it. My '80 Olds Delta 88 has about 167k on it. I just can't part with it. Darn thing burns no oil, body is dyin' but what the heck....it's a dumb car...the only computer in it is in the radio and even that is pis* poor.

I just love tinkerin' with it.

Eric

john hd · 09-29-2003, 06:09 PM

i run the lowest grade fuel that won't ping, knock, run on etc. that's 85/87 for me.

higher octane than needed is just blowing cash out the tailpipe.

john

59toaster · 09-29-2003, 06:10 PM

On mid grade understand the tanker truck does not come with three grades of fuel. It comes with two and the driver mixes the mid grade at the station. THis leaves some room for error. If the driver mixes right then no problem.

The only grades your guaranteed to be absolutly correct is regular and premium.

Friend works at a tank farm and told me that's how it's done.

Octane is the burn rate/ flash point. Basicly the higher the octane the SLOWER it flashes. This is why it helps with ping particulary in a higher compresion engine. It effectivly slows the burn and there for corrects for a lean mix or too far advanced timming. That keeps it from igniting too fast and causing the ping.

Here is a much better definition.
http://theserviceadvisor.com/octane.htm

Basicly you could tun the engine to run fine on regular and get close to the same performance. My take on it is the timing is advanced some. Old hot rodders trick ad yes if you bump the timing and run a higer octane it does work and make more power. Possibly inacurate timing marks on the engine and even though you did set the timing to factory spec the timing is actually advanced. It is not uncommon for GM harmonic ballancers to have the outer ring slip and it usualy slips to indicate lower then actual timming.

GM distributors are also prone to the mechanical advance hanging up (FI equiped vehicles do all the timing with the computer so no worry here). The distributor has a shaft within the main shaft. Vapors from the engine wil get between the two and coke up. This will prevent the mechanical advance from retading after being run at a higher RPM and it will cause a ping problem. Easy to correct if your not affraid to pull the distributor.

Another thing that does happen is carbon forms on the intake valves and pistons. When it forms on the intake valves it acts like a sponge as well as fouls up the air flow into the cylinder. Both will cause a lean problem. this can also cause a little bit of a run on problem because a lean mix has a lower flash point.

When carbon forms on the piston it can have hot spots that will ignite the fuel without spark. This is the usualy cause of run on especialy when coupled with a carboned up valve.

"Top end engine cleaner" from your local GM dealer. GREAT stuff and does clean carbon off valves and pistons quite well.

Silvertwinkie · 09-29-2003, 06:11 PM

John,

I totally agree, however, if you mess with the mix you gotta pay the piper. I have messed with it, so now, I gotta pay for the good stuff and at $2/gal all I can say is...

OWIE!!!!!!

Heck, you got the cash you could make a Buick run NASCAR.

Eric