Better Gas Better Miles

chillinsk8err · July 13, 2007

if i would run 93 octane gas instead of the cheap gas. would i get better MPG. i run 93 octane once in awhile just to clean out my system. but if i would always run 93 would i have better MPG and would it be worth it or would it just be cheaper to run the cheap stuff.

C & A s Dad · July 13, 2007

There are differing opinions on this. I can tell you that I get about .5 to .6 better MPG on 93 but I run it primarily because I tow a camper on occasion and I feel it helps. Most people who offer their opinions on this forum agree that there is a slight advantage to running it in 5.3s. I have never really read anything from someone using it in a 5.7. If you do try it, do not let one tank make your decision for you. You have to run it for a couple of tanks before any difference can be noticed.

I will add one more comment. Whether you are running 87 or 93, name brand fuels will offer some benefit in the area of cleaning. Most base fuels are the same but each company has it's own additive package such as Chevron's Techron. No name fuel will meet govt specs for cleaning agents where companies like Chevron and Shell will have up to 5 times the govt minimums on cleaning chemicals.

Nytemare · July 13, 2007

I think it would be the same...sure you would get better millage, but you would also be paying more. In the end I think your wallet would suffer just as much.

Its like buying a smart car over a cobalt for fuel economy. smart runs about 25 G and cobalts are about 10G.

theoretically;

You pay 400 a month for the smart and 150 for fuel

you pay 200 a month for the cobalt and 350 for fuel....

bottom line its still 550 out of your pocket.

AFD256 · July 14, 2007

I have an 01, and I thought I read somewhere that the engines were meant to run on lower octanes? And there was no beneifit to go high, maybe I made it all up who knows?

Nytemare · July 14, 2007

I know that the ECM will "sense" when you use higher octane fuel due to the Knock sensor. It will adjust timing accordingly and you should get better MPG due to that fact...but is that enough to out weigh the cost of premium fuel?

chillinsk8err · July 14, 2007

well i have the 5.7 motor. i think i am goin to try to run the 93 or something better then 83. i am goin to get the gas from hess. hess seems to work the best in my truck.

Nytemare · July 14, 2007

97 should have a knock sensor. So it should work. But like I said...I don't think the MPG increase will offset any out of pocket cost for you, but your engine will definitely stay cleaner and you should notice more get up and go. In the end...It will be a difference of 5 bucks or so a tank.

Schmids5.3l · July 14, 2007

I don't see how running higher octane fuel would hurt the engine. Theoretically, but also based on cylinder head design, material, cylinder head/combustion chamber temps etc. cast iron heads like mine running 9.5:1 compression should run on premium fuel, but if I had aluminum heads I could run 10.5:1 compression on premium fuel. I have cast iron heads (I'm pretty sure I do anyways), and if I remember right, run 9.3:1 or 9.4:1 compression. IMO knock sensors and computer controlled timing save our motors from melting on 87 octane. I know for a fact my engine runs like a dog on 87 octane... from drag strip ET's, to seat of the pants, to listening to my engine knock and bang at full throttle. During winter I have to run 93 or it will sound like a rattle trap on start up and at full throttle..literally like a food blender full of silverware. I run a minimum of 89 at all times, and only get occasional knocking.

Since the PCM automatically adjusts to octane, it should be safe, but timing isn't a crutch. You can only run so much timing before your spark comes too late and you begin loosing power. Also if the higher octane doesn't burn fast enough your going get maximum pressure too late. I have a link with some decent octane vs compression ratio vs timing info in it. I believe he is a motor cycle tuner.

http://www.factorypro.com/tech_tuning_proc...e_vs_power.html

TheColter · August 9, 2007

You won't gain anything in terms of power of better mileage by switching to a higher octance gasoline other than a lighter wallet. Higher octanes are required for higher compression or forced induction motors. To be completely honest, 87 octane has more energy than 93 octane. the main difference (before cleaning agents and such are added) is that 93 can be compressed to a higher rate before it combusts (pre-ignition).

It's just like people who swear by using 110 octane fuel in thier quads. It does absolutely nothing for performance in a stock motor. I have to run 91 in my quad, which I normally run 93. I've tried 110 and couldn't tell a bit of difference other than the exhaust smelled different. Now, if I upped the compression on my motor, it would run like absolute crap on 93 and could actually damage the motor. I'm using this as an example because it's easier to feel a difference with these smaller motors. My point is that running higher octance fuel in a vehicle that doesn't require it is a waste of money. The only plus you'll get is better cleaning due to the added detergents in pemium gasoline.

C & A s Dad · August 10, 2007

Justin, not meaning to sound disagreeble but when you stated that "93 can be compressed to a higher rate before it combusts (pre-ignition)" is exactly why the 93 works better in our engines. The 9.5:1 compression may not be as high as some of the old muscle car motors but the 93 will allow the computer to run the engine with more advance in the timing, thus creating more power and more mileage. With 87 the pre ignition will come in much sooner than with 93 and the knock sensors will pick this up, tell the computer which will retard the timing. If a 9.5:1 compression engine would run on 87 octane without pinging, then knock sensors would not be needed. The fact is a 5.3 would ping it's butt off with 87 if it were not for the computer and the knock sensors.

I will agree, the difference in power and MPG will be minimal and some people do not feel it is worth the extra money. I use it for two reasons, it seems to help me when towing and I like the extra Techron that Chevron adds to their 93 octane fuel.

I will say again, I ran 10 tanks of 93 in my 3.3 Caravan and it made absolutely no difference. If I am not mistaken, this engine is about 8:1 compression, which is not high enough to benefit from any additional octane. It likely would not pre ignite with kerosene in it.

cmoore74 · August 10, 2007

I also run 93 octane for the following reasons:

- I get about 1/2 - 1 MPG better relative to 87 octane

- Noticably smoother idle

- 93 octane Shell (top tier brand around hear in the Northeast) has the fuel system cleaner in it (I believe 5 times the minimum level of detergeant the government calls for)

- Seems to pull better when towing

Granted the math says I'm still paying more using 93 even with the improved MPG, but it's a small increase relative to my total yearly fuel cost (about $100 extra out of about $3000 / year).

IMO that's a small price to pay to get the best performance and have a cleaner engine.

A tune is in my near future and the benefits of a tune are even larger for 93 octane.

And I agree that while a 9.5:1 compression ratio is not super high, it does call for an octane of about 91 or better to not retard the timing (i.e. to prevent nock).

Not looking for an arguement, this is just my experience and opinion.

C & A s Dad · August 10, 2007

Chris, I have read many posts that agree with our findings. I am like you, I run 93 because I have hard evidence of slightly better MPG and I fully believe it helps me when under load with my camper and I like the added detergents. You are correct about Shells additive in their premium, it is 5 times greater than the min govt requirements. I do not know if it has helped my idle or not, but my 5.3 is so smooth at idle that you cannot feel even the slightest quiver.

The fact is, if my Yukon XL got used on a daily basis and I was not towing with it, I would likely use 87 or 89 and just add a bottle of Techron every 3,000 miles. But, the truck was driven only about 6,000 miles last year and I do tow with it, so the extra cost for the 93 is money well spent to me.

esheehy · August 29, 2007

The problem around here is nobody buys the premium because of the cost, so at any station away from the interstate the premium is 'old' and smells like it. With the MTBE and other junk the EPA requires in the lakeside counties, the gas goes stale mighty quick. I limit my premium purchase to a high volume station right on the interstate for the wifes Denali and my ZX14 Kawasaki which both require it, my 07 NBS VMax with the 6.0 doesnt require it, but will take advantage of it. There are tables in the ECM that specifically address how the motor responds to different fuels, i.e. HiOctane, LowOctane, Gasahol and E85... it automagically detects them and responds with fuel mapping and timing as required. I have seen the tables in my HPTUNER software but I have no idea how or the desire to mess with them.

Long story short, my opinion is that a lot of the time the premium is stale by comparision and may further offset the benefit.

-Devil- · August 29, 2007

in mine .. 07 gmt-900 ... 4.8l ... (motor is still breaking in of course) ... i was using 87 ... and was getting on avg .. 16mpg ... i went up to 93 (from a big station on a main highway) ... and the last two tanks have been 18.9mpg

kewlgye · September 8, 2007

if i would run 93 octane gas instead of the cheap gas. would i get better MPG. i run 93 octane once in awhile just to clean out my system. but if i would always run 93 would i have better MPG and would it be worth it or would it just be cheaper to run the cheap stuff.

I'm not going to get all technical, but my 2006 Z71 CC w/ the 5.3 is getting over 20mpg at 75 MPH. I run name brand 93 octane along with my superchips flashpaq, K&N drop in, and 40 series muffler swap. This is all with 20 inch wheels with 305/20/50's. I can't explain it, I'm getting better than my brother's bone stock 05 2wd CC. Who know's, but I'm happy. Ya'll have a good one.