Official: What are your real world MPG Numbers

[gcd55@hotmail.com]

Ltz sedan 1.8 auto got 4 k on it now have seen 32 MPG on a 1500 mile road trip from Cleveland Ohio to south Carolina and back but mostly see 30-31. My silverado 4x4 was 14 MPG so at 30 MPG I'm quite happy at the 50-55% fuel savings. I am thinking about some mods to get it up to 40.

 

[Larry]

Are you serious?
First of all, BTU is the absolute most ridiculous unit for measuring a fuel's ability to make powerful combustion.
An engine is not a water heater or a dryer.
This is especially true for turbo motors because exhaust gas pressure/energy contribute directly to the car's power.

Second, how are you both asking a question and making a statement?
Yes, running 91 octane allows you to run more aggressive timing which translates into more power.
Ever been in an older high performance car using a distributor with bad centrifugal weights?
The weights spin outward based on engine speed and advance timing - when the weights are stuck the timing won't advance and the power flattens out early in the RPM band.

The horse has been beaten about the dual-map in the Sonic's ECU.
You fill up the tank the ECU uses 'the good map', an aggressive timing map, until it detects knock then bounces you down to the ****ty map.
You could, in theory, stay in the good map if conditions are great ; maybe cold weather, not going to hard on the throttle from stops/high load but I wouldn't count on it.

I don't mean to sound rough, but this issue is getting a little old especially since the benefits of aggressive timing go back to the beginning of motor vehicles.
If there's ever any question feel free to pop the hood on a vehicle and retard the timing and see how the vehicle performs.

Yep, but for clarification 87 has more BTUs than 91/93. Remember that octane is a measurement of resistance to combustion. So for N/A engines, 87 will provide better mpg due to it's higher energy output. The only time N/A really needs high octane is when they use high compression and/or high RPMs.

 

[CoHPhasor]

Yep, but for clarification 87 has more BTUs than 91/93. Remember that octane is a measurement of resistance to combustion. So for N/A engines, 87 will provide better mpg due to it's higher energy output. The only time N/A really needs high octane is when they use high compression and/or high RPMs.

Generally that is correct, unless there have been tweaks to an NA engine that allow it to benefit from aggressive timing, in which case the higher octane is still better.

I'd like to see what the NA's mapping is like and if it has high and low timing tunes like the turbo does.
(As you said, the turbo would benefit much more)

My pet peeve is when people start trashing E85 because of its BTU rating even though on turbo cars there's a great benefit to its exhaust gas energy and resistance to detonation. *sigh*

 

[klystron]

Wow. So glad to see someone understands octane is a resistance to burn. Go Larry.

CoHPhasor is right about E85. Its BTU is lower but the octane is much higher. This allows you to do all kinds of fun stuff to make power! However, if you switch to E85 and want more power you often have to upgrade your fuel system because more fuel is required to make the same power. (lower BTU) So yes, you can make more overall power, but you are gonna need a lot more flow!

BTU is no reason to knock the fuel though there are always advantages and disadvantages. What I hate is the ethanol in our tanks is the biggest scam perpetrated on America since social security. Ethanol is a net energy loss in this country. We put more energy into making it (diesel to harvest and transport, electricity to refine) than we get out of it. We put it in our gas supposedly to "burn cleaner" and for every 1% ethanol we blend our mileage goes down 0.5% and thus we have to burn more fuel to go the same distance. I guess this is another argument, though.

 

[mitdr774]

I have a hatred for E85 from corn. I might tolerate it if it was made from other sources that are far more energy efficient to use.

I know that octane is a measure of its resistance to burn, but also know that if the program has a map for 91 it should be more efficient than 87, especially on a 10.5:1 cr engine. Now if this was a DI engine I doubt it would make a whole lot of difference between 87 and 91, but it isnt. Even my 98 Z24 has always run better on 89 vs 87, and that was only a 9.5:1 cr engine.

 

[sx sonic]

Last tank was a measely 34.XX mpg, I think it might have something to do with the tune and my.right foot, city driving hasn't helped either.

Someone should make a sticky thread about octane and an explantion of what its role in gasoline is, why its used and all that fun techno stuff, so everyone will be informed and the world will be a better place

Since I'm in the mood to share a story (for free) excessively high octane can damage an engine.. I killed a Briggs & Stratton power washer with race gas that was for my bike. Cause of death, burnt exhaust valves/seats. someone should get a laugh out of that! My dad sure didn't think it was funny but what's a kid to do when the washer runs out of gas and the bikes only half clean lol

-tyler

 

[Bogus]

There's already a thread with an extensive debate going on about octanes. lol

 

[sx sonic]

I was thinking more just a technical/factual sticky.

 

[Larry]

I was thinking more just a technical/factual sticky.

In simplest terms, octane isn't a measurement of fuel quality. It is a measurement of it's resistance to explosion. Two different tanks of 93 will not be the same, it all depends on the additives and how much trash is in the tank.

 

[Bogus]

Maybe someone can do that when the debate is finished. They haven't come to a consensus yet. lol

 

[joe truck driver]

I 've never got better fuel mileage from higher octant gas. This includes engines (N/A): fords 122 119HiPo stroker 140 289 289/HiPo 302 352 390 428scj; Chevy 283 307 327 350 342 stroker(8,000 rpm) 396 454; Mopar 273 318 383. (Turbo): Subaru WRX (no chip). However, always better performance in summer. Winter made no difference I could tell by ear. I also had a 54, 74, several 80 cu and currently run a 111cu 10.5 comp (SS /E-type not G carb for torque and mileage) Harley and octane never played well for fuel economy but very important in summer. Would love to see a link for the data to support better fuel mileage based on higher-octane levels when not mashing the throttle.opcorn:


My driving style currently is "old man" for fuel mileage with some exceptions when I just can't help my need for stupidity or just fun. 63 mph unless the air is on and then 60. i drive about 140 miles a dayand split 420 miles into 6 legs. My legs are about 70 miles and only 6 miles are city the other 64 are highway. My current numbers do not look very good either, 5 legs, and the dash gauge reads 48, which means about 43 maybe 44. Have not found reason for worse numbers except temperature and wind which I think would account for drop. Add in winter blend and it makes sense, but I was hoping for better than this with the switch to Mobil 1. It still early is this oil change cycle and it looks like I may see no benefit till another change so I will remain patient without chip and look for patterns.

To get high mileage with the sonic... Any of Them ...lower rpm and slow acceleration are key...but i would like to try the RS. I wish the defroster didn't automaticly kick the A/C on or their was a automatic kick out for acceleration. This would improve fuel numbers as well as drivability.

 

[GeneralZod]

Yep, but for clarification 87 has more BTUs than 91/93. Remember that octane is a measurement of resistance to combustion. So for N/A engines, 87 will provide better mpg due to it's higher energy output. The only time N/A really needs high octane is when they use high compression and/or high RPMs.

Well said Larry, He was on the right track too.

With forced induction, resistance to burn allows for a complete controlled burn. When I found out that the Sonic was rated for regular I was suprised.

It is really easy to see how this works on diesel. I know cetane and octane are different. However, the major factor is when the burn takes place. The less reactive the better the control of the timing. In NJ 40 cetane is the norm. I have used some 50+ cetane, and revving all the way to 5k RPMs and no soot cloud. My theory is that 91 is a better quality all around. Oil companies disagree saying they are all the same quality. I find that a bit hard to believe.

 

[Larry]

I worked in oil refineries for 6 years, they're all refined in the same place. Its all the same oil, just different additives.

 

[ukwildcats]

i have the 1.4 auto. sedan. with 980 miles the dash says 31.5mpg dash also says avg.mph.35.3 I have not calculated mileage after afill up yet.The area that i drive is hilly parts of kentucky.Going on the 1st road trip in the sonic in a week.Roundtrip about 500miles look foreward to see what kind of mpg i will get on the highway with cuz set at 75mph. i will let everyone know.

 

[mitdr774]

Dont expect great mileage at 75 MPH.

 

[GeneralZod]

I worked in oil refineries for 6 years, they're all refined in the same place. Its all the same oil, just different additives.

I know they are made in the same place, doesn't cracking oil get you everything from kerosene to diesel? It is that addivite package that makes the quality. Also, most forced industion require 91 or better. The Sonic doesn't. I think that might change down the road, or at least when the RS starts having engine mods.

I don't think I will be using 87 anymore, unless I feel cheap. But, only in the winter.

 

[GeneralZod]

Dont expect great mileage at 75 MPH.

On the Cruze forum there was a MPG stat verses MPH. We should collectively get some results and sticky the MPG/MPH. That way the same thing won't be stated over and over as much.

I have spoken to many people that think whatever the EPA MPG states is at whatever speed.

 

[sonicBoom55]

Ok after reading the previous pages i still havent truly understood what gas is better for my 1.8
Could someone sum it up?? whats the difference on 87 and 91 and how will they affect my 1.8 Manual
....
Also my cars mpg is telling me 28.5 average mostly city, its a 1.8 manual with about 300 miles on it

 

[cndctrdj]

at 300 miles i dont think your engine has broken in yet. im just over 300 miles and mine has been averaging 37. mostly highway. mostly at 80mph. so im guessing once it breaks in a bit more and i get the better oil in the car i will see better mpg also we have already started to see winter gas up in the north east so that contributes as well

 

[sonicBoom55]

at 300 miles i dont think your engine has broken in yet. im just over 300 miles and mine has been averaging 37. mostly highway. mostly at 80mph. so im guessing once it breaks in a bit more and i get the better oil in the car i will see better mpg also we have already started to see winter gas up in the north east so that contributes as well

Yeah, but I just did my first gas fill this saturday and I put 91 is this ok? previous posts I read said that in the end 91 saved them a few buck because it got them more mpg's but that was for the 1.4t....
I wonder if we get "winter gas" in AZ