Fuel comsuption

[BrettinSanAntonio]

Yes, that's a very good point and is something I need to check in my truck. I've started to get some pinging on hard starts from a stop. I would really like to find the root cause instead of going to a higher octane fuel.

Theoretically 87 should be the best choice, but if you see an increase in MPG then the truck might be retarding the timing on 87 and you don't know it.

 

[landtank]

Any modern car (post mid 1990s) should have a knock sensor that will adjust the timing for engine knock.

Correct, but that can be a retard only system while some will actually advance the timing as well.

I believe our system will only retard the timing if a knock condition is present, it won't advance the timing.

 

[dcFJ]

On my 92, it's looking like I'm getting around 13-14mpg. Hell, it's not a Prius

Damn good mileage for a '92 though...85k...wow! Great price too...considering KBB rates the average mileage for that year at about 97k...and prices around $5800.

 

[Atticus]

Well, if your truck has demonstrated that it gets better mileage on super unleaded, then stick with it. I don't see how it's possible but hey, do what works.

I can tell you from technical experience, reading and speaking with many, many, many mechanics, that high octane fuel is designed to stop "pre detenation" in cars.

When you look at normal engine operation, fuel is sprayed from the injectors into the cylinder where the spark plug fires, at the precise moment when engine components are in the correct position, thus creating the explosion that forces the piston down.

In some engines that run hotter and have tighter specs (and require 93 octane), using low octane fuel will cause the fuel to burn BEFORE the spark plug fires. A high octane fuel is “less” explosive or volatile and will not burn until the spark plug fires.

So, using a higher octane fuel in a vehicle that doesn’t require it yields slightly less power from each burn because the fuel has less “power”.

This is my understanding of the process. I don’t know if I explained correctly but the outcome is correct.

This website for the Federal Trade Commision explaines it better and slimply lays out why premium gas offers no advantage over regular gas for cars that require lower octane fuel.

http://www.ftc.gov/bcp/conline/pubs/autos/octane.shtm

As far as the additive, well, again that's experience and listening to the pros.

I know one of the main ingredients of the Lucas product is alcohol, which, is known to be one of the less effective cleaners in the automotive world. BG44K uses a different base chemical for cleaning and is only sold by garages and distributors much the same way that Amsoil is. It’s a professional grade product.

Do a search for BG44K on the net and there should be some good information about it.

I personally like Seafoam for cleaning parts when I have the engine apart. It works well and isn’t expensive.

Good post. Very informative.

Thanks.

 

[alkaline747trio]

No sir, this is NOT correct. You are wasting money. Do a few simple internet searches on the difference between high and low octane fuel. Your missing the whole point on the purpose of premium fuel and its use. It has nothing to do with fuel economy.

No so, YOU are incorrect. Octane rating is the ability to resist burn/explosion. The higher the octane, the higher your compression and/or more advanced your timing can be. Greater compression or more advanced timing gives more power, if you have more power, you can use less throttle to go the same speed, if you use less throttle then you're improving your mileage. It has to do with power, and power is directly related to economy.

 

[firetruck41]

No so, YOU are incorrect. Octane rating is the ability to resist burn/explosion. The higher the octane, the higher your compression and/or more advanced your timing can be. Greater compression or more advanced timing gives more power, if you have more power, you can use less throttle to go the same speed, if you use less throttle then you're improving your mileage. It has to do with power, and power is directly related to economy.

Point is moot as our Cruisers are not high compression, and do not advance timing though...

 

[alkaline747trio]

Point is moot as our Cruisers are not high compression, and do not advance timing though...

But, you can advance the timing in a matter of minutes to take advantage of the higher octane. And it is only speculation that our cruisers do not advance timing for higher octane fuel, but I believe they do. Why else does my 92 jump from 10º to 14-15º when I remove the jumper. The computer is advancing it.

 

[eurorom]

Well for what ever reason I get better gas milage when i use 92 octane gasoline, I average about 2 miles more per gallon!

Same miles distance in different directions! 86 octane vs. 92 octane

Difference was 2 more miles per gallon with 92 octane.

 

[Aussie]

Sorry Jvasquez, these lads here have lost the point of your post.
For the price and $ this seems like a good deal.
If good maintenence has taken place and you can get it alittle cheaper jump on it.
As for fuel economy forget it, these vehicles scull it.
All the best and let us know what happened!

 

[MyCrush]

FWIW :
I pull 15.5mpg out of my '94 consistently on 85octane. The one time I put in high test my check engine light came on and stayed on 'till i ran that tank out and back to 85. The stealership told me that they are designed for low octane and high test brings up the comp error thus the check engine light.

 

[BrettinSanAntonio]

I'm not sure that I agree. So what you'er saying is advancing the timing will increase your engine's compression? Isn't compression a set value?

I started a new thead so we can examine this issue. I'f I'm incorrect, I'd like to know it. Please chime in.

https://forum.ih8mud.com/showthread.php?t=160442

But, you can advance the timing in a matter of minutes to take advantage of the higher octane. And it is only speculation that our cruisers do not advance timing for higher octane fuel, but I believe they do. Why else does my 92 jump from 10º to 14-15º when I remove the jumper. The computer is advancing it.

 

[BrettinSanAntonio]

True and I apologize. I started a new thread for the octane discussion.

https://forum.ih8mud.com/showthread.php?t=160442

Sorry Jvasquez, these lads here have lost the point of your post.
For the price and $ this seems like a good deal.
If good maintenence has taken place and you can get it alittle cheaper jump on it.
As for fuel economy forget it, these vehicles scull it.
All the best and let us know what happened!

 

[BrettinSanAntonio]

Moving the discussion

Let's move the high vs. low octane discussion to this new thread so as to not high jack this thread.

https://forum.ih8mud.com/showthread.php?t=160442

 

[Martin White]

Don't forget that you need to also factor in the increased cost of premium to your mpg equation. If you get say 5% better MPG but spend 8% more on fuel you are going backwards. The research also suggests that it is a myth that lower octane fuel gives lower MPG.

I've had dozens of vehicles and noticed no statistically significant difference between lower and higher octane fuel in terms of MPG. That's with nearly 1 million km of driving in every vehicle I've owned, and I keep meticulous records. Note I did say MPG, not performance. Some vehicles definitely put out a bit more power with higher octane fuel. And indeed some vehicles give you no choice - you HAVE to run higher octane fuel.

 

[benhunts]

Best I have seen is 18 mpg . But most poeple are getting around 10 to12 mpg. Bill

I'd concur. Just calculated my first MPG on the 93 I picked up last weekend and was a hair short of 12.5.

Ben

 

[zach1234]

just calculated my last tankful,97 450 133k, got 15.5mpg. higher octane gas burns longer, if your getting worse mileage with high octane, something wrong with the fuel system or the timing. the import tuner cars performs a lot faster and do stop better, it still takes a rsx or civic longer to stop going 90 than a 80 going 45. cars that HAVE to run high octane have higher compression ratios(my 07 civic si) 11.0 to 1. the 80 has....anybody? 8.5 to 1? 13 or 14 to 1, youd be running 94 octane racing gas,15 or 16, your lookin at acohol.

 

[Sc0-]

16mpg, 114k '94 with OEM drivetrain running Michelins and cruising at a top of 70mph with regular stop/go traffic.

 

[BrettinSanAntonio]

Higher octane has nothing to do with how long the fuel burns, only with the threshold of when it ignites. The links posted above will explaine how it works and what makes it high vs. low octane. If your truck is getting better mpg on premium, something is out of adjustment or not working properly in your trucks engine/electronics.

just calculated my last tankful,97 450 133k, got 15.5mpg. higher octane gas burns longer, if your getting worse mileage with high octane, something wrong with the fuel system or the timing. the import tuner cars performs a lot faster and do stop better, it still takes a rsx or civic longer to stop going 90 than a 80 going 45. cars that HAVE to run high octane have higher compression ratios(my 07 civic si) 11.0 to 1. the 80 has....anybody? 8.5 to 1? 13 or 14 to 1, youd be running 94 octane racing gas,15 or 16, your lookin at acohol.

 

[zach1234]

that was quoted from the links you posted in the octane thread

 

[psfpilot]

I'm going to look a 92 FJ80 this weekend, asking price $5,000, mileage 85,000. Supposed to be in very good shape. How are these rigs on fuel, specially around the city, this will be the wife's vehicle. Anything in special that I need to look, like leaks in uncommon places, etc...

There's a link to Slee's buyer's guide in the FAQ.
Expect 12mpg and be pleasantly surprised if you get 14 in the city.
That mileage is quite low. We have >264,000 on ours.
And welcome aboard.