I'm back. "Soft modding" a GMC Sierra 1500 4.3 for economy.

[R.W.Dale]

I recently traded my last commuter a notchback 4cyl mustang for a 2000 RCSB Sierra with a 4.3 v6 4L60 automatic, 3.42 gear. I'm using this as a daily commuter for my largely hwy 50 mile round trip daily commute.

So far it's doing really well for a full sized truck averaging 20.6mpg (hand calc) over the past 500 miles driving in a very light hypermile fashion

So far I've done some basic fuel saving mods with the main being the addition of a hard fiberglass bed cover. I was wondering if anyone here has spent any time trying to get the most out of a CPI vortec 4.3 v6 and could offer some suggestions. I'm not looking to go over the top with this project with ecomodding for this truck but I would like to be able to get mileage most folks think is impossible from a full sized truck

[oil pan 4]

You will have to do an electric fan swap. Thats +2mpg right there.

[R.W.Dale]

Originally Posted by oil pan 4

You will have to do an electric fan swap. Thats +2mpg right there.

Really?

I'm surprised at that. I know that for the hotrod side of things they're good for "a few" ponies and it's a popular swap. but I've never really heard of them addressed on the ecomod angle.

[cRiPpLe_rOoStEr]

The truck has a lot of room for improvements. For example, you could get benefits even from forced induction, as it would allow you to keep lower RPM while cruising.

BTW since you already looked at fiberglass for a bed cover, have you never considered one of those single-piece front clips used in off-road racing trucks for weight reduction? Those can be also had a little aerodynamically-enhanced, and that would be good for the mileage in highway.

[Goldenstate]

Achieving the very best mileage from a full size truck is a challenge. Most gains will be small but they will soon begin to add up to some good results. I have been improving my 1999 F 150 since last October.

I started with an antenna delete and synthetic oils in engine, transmission and rear end. Also a synthetic grease in the front wheel bearings. Running the tires at max inflation pressure is always a good choice. When tires are in need of replacement, a high sidewall pressure tire with good LRR can really kick things up. Grill blocks are quick and easy to do. A front air dam is a bit more work but will help. Get rid of all of the excess weight that you can. Spare tire removal from a full size truck is a nice weight reduction. Sure is nice when the fuel gauge slows down or seems to not move near as much.

[oil pan 4]

I think all us truck guys are running electric fans.

[R.W.Dale]

Originally Posted by oil pan 4

I think all us truck guys are running electric fans.

This is the kind of cheap mod with no downside I can get behind.

I had a late forth gen dual e-fan setup in the LS swapped mustang that worked really well and was like $35 at the local pull a part. I will start looking into the swap more.

[oil pan 4]

Find the biggest cheapest fan you can get ahold of.

1 other thing each we all run and do not run.
All the truck guys have gigantic air dams, it cost almost nothing. For me it was good for about +1mpg and it can force more air through the radiator, helping the electric fan mod.
None of have roof racks or sun visors, on an SUV it can cost you 2mpg.

[R.W.Dale]

Where are you typically installing these air dams? Under the bumper or on the bottom of the radiator support?

From your description it sounds like slightly aft of the radiator

[kir_kenix]

My step father bought an early 2000's Chevy extended cab pickup new with the 4.3l. He put 300k on it before he sold it when he retired. It was already "dropped" from the factory and it had a hard, locking cap on it installed by the dealer. He told me the other day that he averaged 22 mpg over the lifetime of the vehicle. He figured his mileage manually every fillup because he was reimbursed for his mileage from his work.

Of course, he drove the like the grandpa he is, nearly always on the highway with a passenger (or 3, he got paid better to haul his co-workers to job sites). I know he didn't have any mods done, but I could swear that it had electric fans from the factory. Most of his mileage was from long hauls from Michigan to the Carolina's where his rail gang worked.

Knowing that, I think that 25mpg would be doable on the highway with some light tweaking. E-fans, max tire pressure, topper/toneau/etc, and air dam should do it. 30mpg might be possible, but it would almost surely require re-gearing, tune, suspension drop, and some more aero mods.