Can you beat this for 6.2l fuel economy...

[mvtofino]

...well, we'll see. I hope there are others who are as happy as I am with how many miles I can go on a gallon of diesel fuel.

I haven't read many threads dealing with a 6.2 liter's fuel economy. I'm sure all the usual rules apply: how it's driven; operating conditions including air temp, altitude, season etc.; city or highway; vehicle particulars & application; aftermarket modifications and so on.

A couple times I've read low teens, and one a few minutes ago of 30+ on the highway that triggered this thread! Wow! 30 plus miles per gallon highway he claims. Is that a US gallon or an Imperial gallon? (A US gallon is only 80% of an Imperial gallon. At 30 miles per Imperial gallon, he would have consumed a lot less diesel fuel than at 30 miles per US gallon. This is one of those very rare times us Canadians come out on top! Ha! But with an Imperial gallon of diesel costing $5.50 or more in Canada compared to a US gallon currently at $3.15 or so, when you do the math, this sense of superiority on the matter is only a temporary illusion of grandeur!)

Not that I'm complaining. But most people I talk to have difficulty believing that I average 20.1 miles per Imperial gallon, combined city/highway driving. This figure was confirmed on a recent 2,400 mile cruise from Vancouver to San Francisco - about 50% on I-5 @ 55 mph (per speedo confirmed by GPS); 40% on Hwy 101 (Oregon & Northern California coasts) @ 25 - 50 mph with lots of twists, turns, hills & chills; and 10% on the Streets of San Francisco with their unbelievable hills!

Our vehicle is a 1983 Pace Arrow motor home with a factory stock, naturally aspirated 6.2 liter "J" code diesel, with a THM400 transmission and a 4.10 rear-end. Michelin XPS 215R85x16 radials up front and Kelly Springfield Sahara Trax 215R85x16 radials on duals out back, all nitrogen filled. The Chevy P30 chassis has approximately 55,000 original miles, and is in very good operating condition. It is driven smoothly, conservatively and respectfully at all times.

I'd love to hear more about the 6.2's fuel economy and consumption from as many other experienced owners as possible. I could sure use the evidence when I get together with my Brother-in-Law who is a career skeptic, particularly when it comes to envious vehicle performance, claims or specifications.

I think 20+ mpg is awesome for a 13,000 pound brick-shaped behemoth at any speed, especially at today's price of fuel! What are your numbers?

Thanks in advance for your replies. Happy motoring this summer...

JT

[Robyn]

Back a number of years, I owned an 82 GMC K5 Jimmy

This little creature would consistantly get 22-24 MPG hwy and 18-19 town driving.

Stock tire sisze with 3.42 gears, 700R4 tranny.

I have an 84 Blazer K5 that I am currently working on and refitting to look like a 89-91 (front clip with side by side head lamps) GMC Grill and GMC tailgate.

Going to set up a 6.2 to J specs with 3.73 axles and 33 inch tires. Likely see MPGs in the 20 range on average.

The 6.2 was a great mileage getter.

Even when a Banks turbo was added they still got great MPG's

The biggy was the small precups used in the heads.

The 6.2 J engine was rated at 160 HP so it was not a rocket, but did a great job.

Have fun.

Missy

[convert2diesel]

Even though I have seen high 30s and a couple of tanks in the very low 40s with the Roadmaster, I find 30 MPG in your rig exceptional. Sure you weren't going downhill?

The one time I used the Roadie to pull my travel trailer (equivalent combined wieght and at least the same enduring aerodynamics) I could only sqeeze out 14 MPG (Imp).

Used to consistantly get 38-40 MPG on an old 5.7 Olds powered Caddy Fleetwood but then I couldn't pull anything with it.

Bill

[NH2112]

My long-gone 85 C1500 w/SM465 & 2.73s and swapped-in mechanically injected (and warmed up) '99 6.5l got a tank high of 24mpg, but average was 22 when I avoided blowing black smoke. Having fun with it still got me 15mpg.

[npauli]

I've had a couple tanks around 27, and a whole bunch around 25.

I drive with a lot of patience - drives my wife nuts.

[Edahall]

I've had a couple tanks around 27, and a whole bunch around 25.

I drive with a lot of patience - drives my wife nuts.

Yup, driving easy is one of the keys to achieving good fuel economy with these engines. I get the best fuel economy between 55-60 mph on my 82 Suburban. These trucks drag a lot of air so keeping the speed down makes a big difference. Also, my Suburban being 1/2 ton, 2 wheel drive, 3.08 gears, automatic overdrive and being strip down with no A/C would help with fuel economy.

The Cummins engine in my 90 Suburban should be a more efficient engine but doesn't quite pull in the fuel economy of the 6.2. I blame it on the lift kit, wide tires, 4x4 and heavy 3/4 ton axles. My recent 5000 mile trip netted 26 mpg average (US gallon) on this rig. I'm looking into designing an adjustable air suspension that would have the ability to lower when on the freeway.

[argo]

Even though I have seen high 30s and a couple of tanks in the very low 40s with the Roadmaster, I find 30 MPG in your rig exceptional. Sure you weren't going downhill?

The one time I used the Roadie to pull my travel trailer (equivalent combined wieght and at least the same enduring aerodynamics) I could only sqeeze out 14 MPG (Imp).

Used to consistantly get 38-40 MPG on an old 5.7 Olds powered Caddy Fleetwood but then I couldn't pull anything with it.

Bill

I am very interested in doing a B body wagon swap in the future, now that my Suburban is just about completed. While all of these mileage specs look good for my Suburban (I haven't yet run a full tank of fuel through it), I am especially pleased with your numbers since I intend to replace a Toyota Camry (great little car, but too little) with a Caprice or Custom Cruiser wagon. I am torn on bodystyles, because I prefer the looks of the square cars, but I see the clearly obvious aerodynamic advantages the later model wagons have. I wonder If a J code 6.2L could pull 35 MPG with 2.73 gears and overdrive in a mid 80s Custom Cruiser, or if the square body has just too much drag?

[phantom309]

my $1000.00 94 k2500 always gets 21+ mpg (canadian gal) its extended cab 4x4 with 3:42's i use it every day for a commuter,gets .8 more with a/c off,.its a 6.5 turbo tho,.
Nick

[argo]

I know it's off topic, so I'll be brief: phantom 309, your avatar is freakin' awesome!

[NetBSD]

im in the lower 20's with mine and it just spun 215,000 miles on it. truck weighs in at 6,040 pound with a full tank of fuel and i didnt notice much drop in mileage with 2ton of stone and flat roads but didnt do much hauling to get accurate readings