Max fuel economy?

[panchosteam]

Thank you guys, MOONDOGGIE: i'm just trying to figure this new to me 1986 6.2 suburban and try to figure the MPG

[Craig M]

Hey Panchosteam, you are in my neck of the woods. That does not sound like to good a mileage for the Suburban. Our 82 has the same gears and 700R4 automatic. Does yours have the TH400 or 700R4? Around town we get around 18 mpg and on trips a little over 20 mpg. We do not go much over 65 mph with it. 75 mph and TH400 would both hurt the mpg, but should still do a little better than 11/12 mpg.

[panchosteam]

Thank you CRAIG M, i found some leaks on this truck so i'm going to have to work them out and go from there,could i do better with 245/85/16 ? or will it be worse? about the trans. i was trying to find out which one i have but i could'nt see the info on it, to greasy , i think i saw something like turbo... i do not remember i will have to check again, any way i'll be checking for mor leaks tomorrow after work
i also found a bad motor mount on the passenger side so after i change it maybe i can see ifthe lift pump leaks. I liked the way my 1984 sierra pick up used to ride with the 6.5 td engine on it so that's why i went ahead and got this other diesel,one thing for sure is that it doesn't ride like my pick up, this suburban been a 4x4 is not comfortable as i expected it to be when i get better mileage on the diesel i'll be happy!

[Truckie117]

Hey guys
Im new at this I have my 99 chev sub 6.5 about 3yrs and have had the pmd changed twice. when I first got the truck it did about 20mpg at 60 since the pump was changed cant do any better than 17mpg at 55 - 60 what could change the milage?
Thanks the new guy

[moondoggie]

Good Day!

I'd bet timing. You might want to get it hooked up to a Tech II or such & find out what the TDC offset is presently. I don't know what TDC offset will produce the best mpg. In fact, I'm not sure anyone does. The good news is that More Power has already purchased his next project truck, which is a 6.5 & will be set up to find out such things.

Blessings!

[FrankJack]

You know, I have spent a few minutes digesting the postings to this mileage issue. I got my engineering degree in electronics/electrical but the facts still remain that increased pumping loses of a turbo will decrease efficency provided adequite air/fuel ratios are maintained. This being said, the additional back pressure of a turbo can produce loses in efficiency in the mid-range area of a diesel engine. If we all agree that the "optimum" range is 1700 to 2100 RPM for the 6.2 then we realize that a trubo will probably not add but take away from efficiency. I.E. lose mileage. At higer RPM's this will not be true and at lower RPM's, there will be no effective restriction. The key here is to have a turbo that will spool up with boost of 1+ PSI after the 2000 RPM and produce about 6-8 PSI at about 2800 RPM. Makes pulling a hill with a load efficient but does not add to the pumping loses at 1800 RPM crusing. All said, the 6.2 is a well balance engine. With a Banks it is even better. Flying a GMC (Brick in the wind) truck is not the most efficient but is an albeit usefull and confortable means of transportation. And anyone that is getting about 20mpg pushing this brick down the road is not doing badly.
If you want gains in mileage, reduce the air friction, rolling friction and increase gearing to the 2.88-3.08 final drive ratios. Back off the boost at mid range, and save the power circuit for pulling at full throttle only.

[Lightyear]

This is all fascinating, especially to a kindergarten-level diesel enthusiast like me. On my last trip Atlanta to Gulfport for weekend ANG duty, I got an average of just under 19MPG calculated over three fuel stops (not knowing availability of #2 on the Gulf coast). That's in my '88 6.2 Banks 4wd with a non-functioning TCC. Kept it at 65 or below as much as possible. The trip took a little longer, but my wallet wasn't as light afterwards.
I really appreciate this forum; it's a great way to learn about these neat old beasts.

Buzz

[mhagie]

Just put ol blue away for the winter, last two tanks average 19 mpg @65 mph back and forth to work 65 mile rt.
won't complain with this mileage, think it would hit 20 w/out the town portion.
Now if I can find my STA-BIL I'll be set.
Merle

[perch]

Hi,Just my experiance,1989,6.2, chevy 4 by 4,2500,running boards,3.73,262000 miles,

temp.20, At 55 tail gate open 22mpg
temp.70 at 55 tail gate open 24mpg best ever
at 65+ 19.3 tail gate closed.
short trips,farming,haul,pull trailer,my normal 16.3mpg

Merry Christmas
Butch

[More Power]

Well, a logistical challenge has been overcome, and the 6.5L El Camino project will begin soon.

As soon as I acquire a couple decent images (of someone elses Camino) to use as a lead-in for the introduction, I'll post a new article that outlines the project, and hits the highlights for maximizing fuel economy.

For now, you can visit the following link to see what a 1972 Chevrolet El Camino looks like.

Link

Jim

[AndyL]

Jim, I am plannin' on giving you a run for your money in the Olds! At least on mileage

[More Power]

The Max fuel economy project has begun! While this will be a max mpg project using a mechanically injected non-turbo (to begin with) 6.5L diesel, much of what will be discussed can be directly applied to all 6.2/6.5 diesel equipped vehicles (including some aspects of a Duramax equipped truck as well). We may even be using some 6.2 specific components…

Things like engine rpm, vehicle weight & drag, and driving strategies for max fuel economy will apply to just about any light diesel. Our vehicle choice will allow us to explore what effect weight and drag have on fuel efficiency.

I think you'll be surprised at what components are available for all 6.2/6.5 diesels (EFI and MFI) that were designed to improve fuel economy, and we'll be discussing them in future Project MPG updates. Some components you may already know about, but there are a few you probably don't… At least not yet!

Jim

[HANK1948]

MP,
What ever happened to the 6.5 powered s-10 blazer you talked about in Florida? Ive always wanted to do something like that because Iam sure it could get 30+ MPG

[More Power]

It was one of those phone calls - like many I receive - from a member who told me what he had done. I asked that he send some images and discussion to let more people know about his project. That's where it is... We'll wait & see...

I'd like to see it here, cuz it adds to what we're doing with fuel economy.

Jim

[rjwest]

My early 82 ( delivered in Nov81 ) 3/4 2w
4 sp std tran w OD, ( weighed 5500 lbs )

24 MPG, always, drove truck to 230K miles
( 1 rebuilt pump ) sold it and it ran more miles,

I would note that the fuel back than was
heavy,yellowish, and not as much foam...
Ah, Progress... ( house oil ran good also.)

[More Power]

6.2L/6.5L Fuel Economy
Cylinder Heads & Ricardo Comet
Part II

The 6.2L diesel engine was introduced during a time when the world energy market sent fuel prices skyrocketing. While it may surprise you, gas & diesel pump prices during the early 1980's were actually higher than they are now - when adjusted for inflation. GM's 6.2L diesel was designed and developed for tight fuel supplies and high pump prices, and we may need to revisit the 6.2/6.5 to help provide a solution to the high fuel costs we're seeing now. The early light-duty 6.2L diesel powered trucks would consistently deliver 22-24 mpg when driven conservatively, while the later light-duty 6.5L turbodiesels produced 5 or more miles per gallon less. Why is that? The answer to that question is what we're investigating this time.

[DanSSj4]

I have a '92 GMC Vandura 3500 work van I go as fast as 75 mph Max(Rarely) never tow with it, have 2 3500 6.5 TD 93 & 97 It currently runs a wore out 350 in. Gas Engine I want to convert to diesel for equal or a little bit more torque but better gas effieiency what would work best for suck a heavy, large, non airodynamic brick.

Also on another subject the housing for my Differential is damaged where the driveshaft comes in and there is extra play it bangs sometimes. I plan on just replacing the whole rear end with a newer lower milage one What readend would give me the best Fuel Economy, power is unimportant because I drive the van REALLY Slow

[djw32]

More Power,
The 6.2/6.5 article is great! Please keep the articles coming.

[Overdrive440]

I have just stumbled across this forum. I am trying to get away from the uncomfortable and noisy ride that is a small 4 cylinder econo-car, but I want to keep the high fuel economy (or close to it). I can't wait to read more on the El Camino project.

[woodywp]

I owned a 1982 K1500 SWB 6.2 with a manual 4 speed with OD and 3.42 gears. This truck broke 30 mpg on several ocassions driving at 58-60 mph and doing my very best to be smooth on the pedal. I would build a little speed down hill at let it fall off some on the next hill. This sounds to good to be true now but I always fill up to where I can touch the fuel in the neck of the filler. Having since owned 2 other 6.5 turbos a 1994 K3500 LWB 5 speed manual 4.10 18.5 mpg and 1995 2500 Suburban 4 speed auto 3.73's 18-20 mpg I would say 6.2 NA without a doubt. I would really like to have my old truck back now with fuel prices what they are.