View Full Version : Silverado Big Block Owners(8.1 liter)

06-06-2003, 12:59 AM
Thinking about a silverado 2500 HD with the 8.1 liter. Is this a monster or what? What kind of realistic gas mileage can you get out of it? Any problems or complaints on thus motor? All comments appreciated----Mike

06-06-2003, 01:06 AM
I'm sure you can find some good opinions on that truck and engine here, but you can probably find out more at www.pickuptruck.com
I frequent that forum quite a bit, and from what I hear most guys with the 8.1 get around 12 mpg or so unloaded. If memory serves me right, I think I remember someone saying they got nearly 15mpg, which is great for that size engine. From what everyone says, this powertrain is a heck of a puller. If you decide to visit that site, post your question in the GM truck forum. You will have to register for the forum, but it is quick easy and free just like lawnsite.com. Best of luck.

06-06-2003, 02:32 AM
9mpg loaded or unloaded, headwind or tailwind.

CO.d 502nd
06-06-2003, 06:31 AM
When i was still in partnership with my brothers we had the big block ,its a beast allright haul a mountain but look to get po mileage at best.Dang good motor though.

06-06-2003, 06:47 AM
Bluebeard is right. With an engine that size she doesnt know if you have a loaded trailer behind you or not- gas milage is near the same regardless. Is that a gas engine? If so you might want to go diesel for a motor that size.
Damn near twice as big as the engine in my rig.

06-06-2003, 07:08 AM
Great engine. Not quite sure they needed to stretch it to 8.1 Liters though. That extra 42ci, while I'm sure is nice, probably isn't needed if they were to simply tweak a few things on the old 454.

I really am not a big fan of the new Allison or its pricetag. I really AM a fan of the new Duramax, however between the Allison and the Duramax, I can buy a brand new Lazer! WAY too much of an upcharge for an engine/transmission option IMO. If I'm going to pay THAT much for a Diesel option, it better be a HO Cummins under the hood!

Ideal combo would be the 8.1 and the 4L80E (they offer it in the Suburban). I'd buy one in a second as its only an $800 option.

If I were you I'd look at what the 6.0/4L80E is capable of. And if it will meet your needs. It's no slouch, but if your going to be towing heavy every day (large enclosed trailer, etc) it may not be for you. You really need to wind the 6.0 up a bit to get it to work.

If your buying a BIG BLOCK truck, fuel mileage should NOT be on your shopping list! People have been asking me my Big Block mileage since 1989! Best was 12 worst was 5.

06-06-2003, 07:34 AM
I own an 2002 2500HD 4X4, 8.1, Allison Auto. Upgraded from a 2000 Z71, Auto OD, 5.4 (327)

I am very pleased with my truck. Plenty of motor to compliment the Allison Auto. Tran is electronically controlled to shift when needed and also will downshift going downhill to save your brakes. I bought as a work horse. No carpet, vinyl seat, A/C, and a radio is about it. Paid $29 something interest free money. 8.5 mpg working and 9.8 mpg not working.

No regrets on the upgrade............good luck.

06-06-2003, 12:58 PM
I have a 2002 GMC 2500HD, 8.1 Litre 5 speed Allison with 3.73 gears. Running unloaded I get around 12 mph. Have not checked the mileage loaded. Does appear the gage moves to empty a lot quicker when loaded

06-07-2003, 12:25 AM
Originally posted by TLS
Ideal combo would be the 8.1 and the 4L80E (they offer it in the Suburban). I'd buy one in a second as its only an $800 option.

Actually the 4L80E is standard for the 8.1L engine. You have the option to upgrade to Allison for extra $$. You can get 4L80E with 8.1L on 2500HD and 3500. :cool:

06-07-2003, 02:24 AM
Originally posted by wxmn6
Actually the 4L80E is standard for the 8.1L engine. You have the option to upgrade to Allison for extra $$. You can get 4L80E with 8.1L on 2500HD and 3500. :cool:

That is incorrect. When you get the 8.1 in the 2500 HD or 3500, you must get the Allison auto or the ZF 6 spd. The 4L80-E is available in the 2500HD and 3500 dooley with the 6.0 only. If you opt for the manual trans with the 6.0, you get the NV 4500 5 spd. Now, if you want a big block 8.1 in a Suburban 2500 or the Avalanche 2500, you get the beefed up version of the 4L80-E, which is called the 4L85-E. The reason behind this is because the Allison is too tall to fit in the 'Burb or Avalanche. If you get a chance sometime, compare the frame height of a 2500HD to a Suburban 2500. You will see the frame rails are much taller in the truck as opposed to the Suburban. That is why the Allison won't fit in the 'Burb. Hope this helps.


06-07-2003, 09:11 AM
Forgot to mention...At the time I bought my truck, GMAC had a promotion to anyone with business lic...Free aluminum tool box retailed at over $400.00 scoops. And they will install it for free.
They won't mention it but will give if you ask. A friend told me about it just before taking delivery.

06-07-2003, 11:34 AM
pottstim - I just checked the GM brochure and I see that you are correct. I am not sure where I got that idea from, but it is a good thing I know about it now. :)

06-07-2003, 01:11 PM
wxmn6, no problem at all. :) I have always been a big fan of GM, and I try to keep on top of their products by picking up all of the lates sales brouchures, etc. It's pretty sad when you visit some of the dealers and know more about the products than their salespeople do. :rolleyes: I guess they just don't take their jobs too seriously.