is this safe?

[jethro_3]

5.3 w/3.42 and 87/89 tune and I get better mpg with 93 oct, go figure....

[skipr]

Originally Posted by BowtieX3

Your Owner's Manual has factory suggested fuel recommendations. It will say what you should run...however, keep this in mind...the higher the octane, the cleaner the fuel, meaning the more complete burn you'll acheive, meaning the better mpg you'll get. You'll also have less carbon running through your engine, less potential for future problems. Uncle works for Exxon...take it for what it's worth.
I know prices at the pump are horrendous (I have to run 93...6.0 HO). If you do run 87...twice a year I'd run a cleaner like the Chevron concentrate through a tank...my two cents worth!

What does your uncle do at Exxon? I worked at GATX (west coast) tank storage and truck terminal facility. Exxon distributed there fuel from there because there is no Exxon refinery in Los Angeles area. They bought fuel from Texaco refinery and mixed in a light oil type substance called "Exxon Additive". Now they can call it Exxon fuel. And Ultramar would add denatured alcohol to there fuel to displace the water soluable impurities.Ask uncle what the hell is that additive, looked like used motor oil to me.Or is it a trade secret like the formula to Coke Cola?The only fuel that required quality control was the Military JP4 jet fuel.The rest... just take a sample get the API specific gravity, flashpoint, and store sample for 3 months.

[GMMerlin]

Your vehicle was designed and the calibrations are set to run on 87 octane fuel...using a higher octane fuel can cause some unwanted driveability concerns.

Your Owner's Manual has factory suggested fuel recommendations. It will say what you should run...however, keep this in mind...the higher the octane, the cleaner the fuel, meaning the more complete burn you'll acheive, meaning the better mpg you'll get. You'll also have less carbon running through your engine, less potential for future problems. Uncle works for Exxon...take it for what it's worth.

Actually the higher the octane, the slower the fuel will burn (this is the reason engines with detonation concerns or high compression engines run higher octane fuel...the resistance of the fuel to burn means it will not preignite before the actual timing event occurs)
Since the fuel is slower to burn, this means that engines that are not designed to burn the higher octane fuel could begin to form carbon deposits and this leads to detonation , cold start and misfire concerns the longer the higher octane fuel is used.
The carbon deposits form on intake valves and on the pistons..the carbon absorbs the fuel as it enters the combustion chamber and causes a lean air/fuel ratio the can cause a lean misfire concern.
Also as the carbon absorbs the fuel, more carbon deposits are formed and the cycle keeps going.
On the engines where people are complaining about "piston slap", this is a condition caused by carbon deposits on the piston..when the engine is cold, the carbon is hard and this is where we get the knocking noise on cold starts...as the engine warms up and the carbon absorbs some of the fuel and the carbon softens and the knock goes away ( until the engine cools down again)
My advice..use only the grade fuel recommended for your application and find a gas station that has "Top Tier" gas, this is gas formulated to prevent engine deposits.
For more info Click here

[twomorestrokes]

Originally Posted by GMMerlin

Your vehicle was designed and the calibrations are set to run on 87 octane fuel...using a higher octane fuel can cause some unwanted driveability concerns.




Actually the higher the octane, the slower the fuel will burn (this is the reason engines with detonation concerns or high compression engines run higher octane fuel...the resistance of the fuel to burn means it will not preignite before the actual timing event occurs)
Since the fuel is slower to burn, this means that engines that are not designed to burn the higher octane fuel could begin to form carbon deposits and this leads to detonation , cold start and misfire concerns the longer the higher octane fuel is used.
The carbon deposits form on intake valves and on the pistons..the carbon absorbs the fuel as it enters the combustion chamber and causes a lean air/fuel ratio the can cause a lean misfire concern.
Also as the carbon absorbs the fuel, more carbon deposits are formed and the cycle keeps going.
On the engines where people are complaining about "piston slap", this is a condition caused by carbon deposits on the piston..when the engine is cold, the carbon is hard and this is where we get the knocking noise on cold starts...as the engine warms up and the carbon absorbs some of the fuel and the carbon softens and the knock goes away ( until the engine cools down again)
My advice..use only the grade fuel recommended for your application and find a gas station that has "Top Tier" gas, this is gas formulated to prevent engine deposits.
For more info Click here

Thanks Merlin. I agree with your octane statement 100%. You are not doing your engine (or your wallet) any favors by using higher octane than you need.

Although I question your statement on piston slap. At the dealership, we were replacing new engines under warranty for this situation before GM released bulletins stating that this was not a longevity concern and to NOT replace the engine for this noise.

[xedin0]

Well, I know that after I installed my K&N FIPK and catback I ended up getting 2mpg more with premium than regular.

At 15k a year I actually save money by using premium even though it seems more expensive initially. Similar to what was posted above. My milage was close to 15mph with my 4.8 and now it's averaging a little over 17mpg.

Doing the quick math...
15000 / 17mpg = 882.35 gallons (92/93)
882.35 gallons x $2.70 = $2382.35 a year

15000 / 15mpg = 1000 gallons (87)
1000 gallons x $2.50 = $2500

That's almost $120 a year in pocket savings by switching to premium with my FIPK and exhaust. Plus I'm helping the environment by running cleaner AND I'm using over 100 gallons less gas a year.

The numbers may bit a bit different between 89 and 87. I can only speak of my personal experience however so I hate to make any assumptions. The #'s are really tight so I would definately evaluate my gas milage at the different levels and see what kind of increase you get before making a final decision. Just to help you do a quick calculation in your head... The break even point between the fuel prices is right around .6mpg for ever increase of $.10 per gallon. This would mean you would need to see a 12 mile per 20 gallon performance increase to break even with 89 or a 24 mile per 20 gallon performance increase at 92/93.

In my case the performance increase was closer to 45 miles per 20 gallon fillup so it was definately worth it to me.

[twomorestrokes]

You guys are going to make me bite the bullit and spend the money for a tank of hi octane to try for myself, aren't you?

[White Lightening]

Greetings Xedin0,

And - the spread between premium and regular becomes less and less important as the gas prices rise. At $2.70 for premium and $2.50 for regular - just simple numbers show you need very little improvement to justify - compared to $1.70 premium and $1.50 regular

[intel_guy]

Originally Posted by White Lightening

I did a calculation as follows:
If a truck owner drives 15,000 miles per year averaging only 18 miles per gallon using 92 octane and the difference in gas price for 92/93 to $2.70 per gallon versus $2.50 for 87 octane fuel. Lets also use the fact that the average (MPG) would go from 18 (with premium) to 17 (using regular). The actual net difference in cost ====== $45.00 a year.

As a result - it seems it would not pay to switch to lower octane. In my area - the difference in price from premium to regular is only 12 cents a gallon where I get gas. However I had used 20 cents in the calculation - to even try harder to favor regular. Even under those conditions - $45.00 just isn't worth the difference in my opinion - I'll stick with premium till it cost justifies a switch.

My VW Golf TDi gets 50mpg, Diesel Fuel @2.35/gal = $705/year for 15k mi., saving me $1500/yr compared driving my 99 Silverado the same distance. I guess that figures to .10/mile savings over my weekend toy.

[xedin0]

Hmm. Good point there WL. I didn't really look to hard at the lower end of the spectrum. There is definately a point of growth in there where the more expensive the gas the easier to justify. Looks like using the $1.70 and $1.50 example I would barely break even between premium and regular with a 2mpg increase. Of course if gas was back to that point I would be more than happy to pay the $.20 diff a gallon since cost in gas alone would be $850-1000 less a year than what we're liable to pay now... It's to the point now where it seems like the economy would do better to start buying nothing but premium and say screw regular unleaded.

Figure this. One 42gal barrel of crude oil (in addition to other things) makes approx 19.5 gallons of gasoline. If 500,000 people bought nothing but premium unleaded this next year that could average out to 100 gallons less per person fairly easily. Breaking that down thats over 2.5 million barrels of oil that could be saved in a year. Even if oil dropped back down to $40 a barrel that's still $100million a year that staying domestic in addition to any savings we the consumer may get out of it at the pump in mpg benefits. Granted I'm probably missing a bigger part of the picture but it seems to me even that's being conservative.

[jeverett]

I average way over 15K a year. I can't afford to fill up anymore wiht my income using 93 octane. The gas down here where I am now is 2.71 for 93 octane. Thats damn insane. I just talked to Nelson and he's sending my 87 tune tomorrow thank the Lord.

[xedin0]

Are you sure Jeverett? How much is it for regular 87? It's real easy to put the #'s to the test... Especially if you're getting a Nelson tune. If you think about it the cost diff between filling up with 92/93 and 87 is around $4. That's not even 2 gallons worth of gas at that price. I'm assuming your 87 is around $2.50ish? If you're willing to spend the money on a Nelson tune you're probably looking for more performance and/or better gas milage. Depending on what kind of results you get with both grades you could end up playing the "Pay me now or pay me later game". A 2mpg diff between 87 and 92/93 at 20k miles is over $150 a year in savings with an increase in performance. With the quality of gas deteriorating like it has in the past 10 years and the cost rising, everyone is looking for a way to save money.

I can't say that my results are the same as everyone else but I do know that anyone can get them with their Silverado and mine are nowhere near the best I've seen. My dad's Ford gets over 3mpg diff between regular and premium and he sees the diff a lot more than I do on a monthly basis. I would definately double check and see if you get any diff between the two after your tune. You may be surprised.

[BlenderWizard]

I have an '02 5.3L that, even when stock pinged with 87 octane. I have since goten a 87/89 Nelson tune, and have had to get Allen to retard my timing once to compensate. The pinging is gone except for at high RPM (top end of each gear at WOT). Any ideas what is going on?

[jeverett]

I've had a Nelson 93 octane tune since last October. It really woke the truck up, but didnt do a thing for the mileage really. I was told it would increase a few mpg. The power was unreal but it got the usual 16-17 mpg. I was getting that with 87 octane before I got the tune. I talked to Allen yesterday and he said that this tune was his economy tune and should result in a bit more mileage. I'm also having some extra Torque Management removed so more power goes to the ground.

[BlenderWizard]

Originally Posted by jeverett

I've had a Nelson 93 octane tune since last October. It really woke the truck up, but didnt do a thing for the mileage really. I was told it would increase a few mpg. The power was unreal but it got the usual 16-17 mpg. I was getting that with 87 octane before I got the tune. I talked to Allen yesterday and he said that this tune was his economy tune and should result in a bit more mileage. I'm also having some extra Torque Management removed so more power goes to the ground.

You might also talk to him about leaving the throttle body open during shifts... he told me it has a similar effect.

[jeverett]

Hmm. Didn't know you could do that. I asked him if there was anything else that would help and he didnt mention anything. I had my rear o2's turned off so I can remove my cats soon. They're clogged up, so that will help also. No emission testing here at all, visual or otherwise.