Fuel economy: 1999 Tahoe

[Edahall]

An inline diesel is nearly unbelievably frugal, even in big trucks. There is no wasted throw in the rods/crank that all V style engines have and the power output of diesel fuel means much less can be used to make more power than gasoline. No ignition means less chance of electrical failure and no distributor to foul. I've been ******* after 4HK1 powered OBS for years. If I had the pocket book to build it I promise you I would.

Believe it or not, the old 6.2L diesel in my 1982 Suburban pulls slightly better fuel economy than any 6BT Cummins I've owned. However, the Cummins has a lot more power and were in a heavier 4x4 truck.

 

[Tempted]

Yeah but as far as diesel engines go the 6.2 is junk. No power, not reliable, crappy fuel delivery system, not able to *reliably* add forced induction. Also heavy and don't rev, even in diesel standards.

 

[Edahall]

Yeah but as far as diesel engines go the 6.2 is junk. No power, not reliable, crappy fuel delivery system, not able to *reliably* add forced induction. Also heavy and don't rev, even in diesel standards.

I think you may be confused with the 5.7L diesel engine GM released in the late 70's. They were exactly like what you described. The 6.2L even today has a loyal following and are known for being more reliable and fuel efficient than the 6.5L. The 6.2L in my 1982 Suburban has been so reliable and long lived that it has outlasted the rest of the vehicle. Yes it doesn't have much power but it gets me where I want to go without guzzling fuel.

 

[Tempted]

I remember the Olds 350, as well as 4.3 V6 diesel engines quite well. They mainly powered cars. The 6.2 Detroit was a 100hp boat anchor in most respects. It did get a little better fuel economy at a time when diesel fuel was loaded with impurities and and cheaper than gasoline AND while the auto manufacturers were struggling to build an engine that would pass new EPA regs and make any power. Since then engines have become a hundred times cleaner and make more power than that 6.2 could ever dream of. And you can realistically expect 20-25mpgs from that engine but at a HUGE cost in power when compared to the Vortec 5.7. And now that diesel fuel has, as ridiculous as it is, surpassed gasoline prices the benefit of any diesel conversion has been reduced. The 6.2 just doesn't make any sense as a replacement for a 5.7 Vortec. The higher MPG is negated by the higher fuel price so there isn't any upside there. And to swap a lower performance engine into a vehicle without achieving lower operating costs isn't something anyone I know would want to do.

All of that said, the other thing to remember is that this swap is 100% illegal to use on the street.

Per EPA: "For light-duty vehicles, installation of a light-duty eng~ne into a different light-duty vehicle by any
person would be considered tampering unless the resulting vehicle is identical (with regard to all
emission related parts, engine design parameters, and engine calibrations) to a certified configuration of
the same or newer model year as the vehicle chassis"

 

[5spd Z71]

Not to mention its illegal to put an older engine in a newer car...

Might as well get a 5.7 Vortec and build it for MPG's

 

[Edahall]

Not to mention its illegal to put an older engine in a newer car...

Might as well get a 5.7 Vortec and build it for MPG's

Good point. If I stay with the 5.7 Vortec, it'll be the only vehicle I own that is not illegal. So what do I need to do to bring the fuel economy up from the 16 mpg highway EPA estimate to something I can live with like 20 mpg?

 

[Tempted]

Might as well get a 4.3 and strip all the interior. Buy skinny and light wheels and tires. Ditch the AC, power steering, spare tire, audio system and anything else that the truck doesn't have to have to run. Reduce the alternator to a 20 amp drag only unit, strip all sound deadening material and go on a diet to reduce driver weight. Actually, wear only fishnet clothing as well, its lighter. And all of that will still be easier and more practical than the 6.2.

 

[Swaggerwagon]

The Suburban gets 28-30 mpg

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