20 mpg on a '94 K2500 454 w/ 3.73 rear end

**AndyD** · 09-01-2006, 03:54 PM

My mission is to get my suburban to 20mpg combined city / highway. So far I'm getting about 13 with a tune-up due anyway and all stock parts.
I think it's possible with better air intake, exhaust, filters and ignition.

Does anyone have experience with a msd ignition control box like the 6a? Also, to maximize the effect, what distributor, spark plugs and wires are the best with that? What fuel filter is the best?

By the way, I put in a K&N air filter and turned the air cleaner lid upside down. That easy trick helps quite a bit with acceleration, and it also makes the truck sound much cooler. I haven't measured yet, but it seems to help gas mileage too. I also just ordered a throttle body spacer that lifts the throttle body up 1 inch. I'll post my experience with that once I put it in...

**Steve** · 09-03-2006, 05:50 PM

That's a lofty goal, let me know if you get there!

**AndyD** · 09-08-2006, 10:30 PM

I don't really know if that's really possible. I think I would be happy with 18 or 19 as well.

With some of the advancements in the last 20 years in motor mechanics and a well tuned engine it should be possible to improve gas mileage and emissions.

**gmcjohnny** · 09-09-2006, 06:55 AM

msd is nice but jacobs makes a better system thats easier to set up you can even call them with questions an thell walk you though it johnny

**unplugged** · 09-23-2006, 08:40 AM

Originally Posted by AndyD

I don't really know if that's really possible. I think I would be happy with 18 or 19 as well.

With some of the advancements in the last 20 years in motor mechanics and a well tuned engine it should be possible to improve gas mileage and emissions.

It is possible:
Active Fuel Management™ technology helps the 2007 Suburban equipped with the Vortec 5.3L engine deliver an estimated MPG of 15 city, 21 highway for 2WD models and 15 city, 20 highway for 4x4 models. In fact, you can drive up to 651 miles on a single tank of gas in 2WD models

Just drop in a 4/6/8 engine out of an 07 and you're there! (That's if you believe GM's advertised mileage figures)

Like all good adventures, be sure to have fun!

**AndyD** · 10-15-2006, 02:59 PM

I think I read a thread right here on this forum from somebody with a '07 2500 6.0. He says he gets 9mpg city and 13 mpg highway?? Anyway, I just checked after a longer roadtrip through the mountains in Montana. With about 66% highway/interstate at 75mph and 20% city driving I got 16mpg. I don't know how that compares to other 'burbs but my brother in law with his '95 2 door Tahoe only gets 13mpg.
Andy

**Steve** · 10-26-2006, 09:44 AM

Originally Posted by AndyD

I think I read a thread right here on this forum from somebody with a '07 2500 6.0. He says he gets 9mpg city and 13 mpg highway?? Anyway, I just checked after a longer roadtrip through the mountains in Montana. With about 66% highway/interstate at 75mph and 20% city driving I got 16mpg. I don't know how that compares to other 'burbs but my brother in law with his '95 2 door Tahoe only gets 13mpg.
Andy

That's pretty fair. Fuel mileage has gotten better over the years, that's for sure, it's just that vehicles are getting heavier and have better performance. If they cut some weight and manage accelleration better (slower 0-60 time) they could get mileage up to that level. People would say that it's gutless though, so it's a double edged sword.

**AndyD** · 11-01-2006, 03:51 PM

If they cut some weight and manage accelleration better (slower 0-60 time) they could get mileage up to that level.

Yes, that is true. In Germany as a student I had a '86 Golf Diesel. 54hp and a 4 speed manual. I don't think it was faster than about 90mph, but it always got over 50 mpg to almost 60 mpg. No matter if I was driving in the city or on the autobahn. Of course it didn't have AC or power anything, in fact it didn't have a trip counter or a middle console either.... but it was cheap to drive. In Germany we have paid over $6 per gallon for the last 10 years, so gas mileage counts.
I think it's sad that car makers don't make cars like that anymore. It was perfectly fine foe city driving and much cheaper and more durable than any of those new hybrid cars with better gas mileage. The technology is there, we just don't use it.
VW in Europe offered a car some time ago, smaller than a Golf, that in real driving conditions got up to 84 mpg. It wasn't too comfortable and a bit more expensive than than the standard model, but still hybrid cars can only dream of those numbers.

**curtolson** · 11-27-2006, 11:57 PM

Andy the site engineer sounds intelligent. Then I read the question and laughed very hard.
I purchased a 95 K2500 with the 454. MPG is really not an issue when one purchases a 8600 lbs truck with 4wd and a 7.4 liter engine. RAW power and braking is the concern.
If I must answer this ? it would be save the money you would spend on the aftermarket parts to obtain a better mpg and use that same money to purchase fuel. The time you spend working on the aftermarket parts has a value. Investors call it the time value of money. Really Gas is cheap.
Time is priceless. Enjoy your 454 it's a great beast.

**TrailLeadr** · 11-28-2006, 09:00 PM

While time may be priceless, you'd be hard pressed to convince a 'burban enthusiast that spending time modifying their baby is not time well spent. I'm currently rebuilding my 454, and I'm looking at this as a labor of Love. Don't tell my wife that though...

As far as doing something positive to affect your mileage you might consider changing out your rear diff. Odds are you have a 4.10 rear, drop it down to something in the low 3's if possible. You might see a power difference in towing, but if you don't tow you'll see a marked improvement in mpg.