GMC Sierra vs P71 mpg?

The internet shows my 2006 Sierra crew cab 4x4 5.3 gets 16/20 while a 2003 P71 gets 16/22.

Sierra weighs ~5,200

P71 weighs ~3,781

What gives?

Actually getting the claimed numbers is far different thing. I think the p71 will probably be easier than the truck. 

In reply to Dusterbd13-michael :

My issue here is that I have a hard time believing that the P71 is so bad. I understand what you’re saying but how can the estimated figures be that close? I’m spending like $70 a week for gas just for work. I figured the P71 would be a bigger savings than this.

(What I mean is if I bought a P71, I’d expect to see a bigger savings in gas purchases over the truck)

In reply to ebonyandivory :

Do you really need a truck for work ,is a work truck,or are you just commuting it to and from work?

Well, for what it's worth, my 200k mile old p71 was getting 22 around town and 25-27 at 70 on the highway. 

Alfaromeoguy said:

In reply to ebonyandivory :

Do you really need a truck for work ,is a work truck,or are you just commuting it to and from work?

It 99% a commuter right now though we use it for truck stuff here and there. 

I’m giving my truck to my son. I’d be selling if if he wasn’t about to get his license.

The civilian Crown Vic gets better mileage due to the lower numerically rear gear.

RossD said:

The civilian Crown Vic gets better mileage due to the lower numerically rear gear.

But the P71 and the truck have similar ratios however. Truck is like a brick compared to the P71. And even the tires are better for mpg on the Vic too. It don’t make sense.

Two other possibilities: Is the truck a six-speed vs the P71's four-speed?  Also, I bet the truck spanks the car in low-speed torque, which potentially means you have to rev the truck less during a commute.

In reply to Stealthtercel :

4L60e - 4 speed auto.

P71: Tq 287 @ 4100 RPM

Truck: Tq 325 lb.-ft. @ 4000 RPM

Truck is way heavier, remember.

Huh.  13% isn't much of a spanking, is it?  OK, I'll stand over here with the other confused people.

Stealthtercel said:

Huh.  13% isn't much of a spanking, is it?  OK, I'll stand over here with the other confused people.

Can I politely ask you to clarify this? Are you saying 13% is NOT a big difference or it is? What about this is confusing? Again, no sarcasm intended, seriously.

Put the truck drivetrain in the P71 and see what happens. 

The P71s have never gotten very good fuel mileage. Mine gets 17 around town and 22 on the highway. At a guess, the truck does better because the Chevy engines are simply more efficient than the 4.6 in the Ford.

If you are chasing fuel economy, buy an economy car. My daughter just bought a Sonic LTZ to replace her Super Coupe and went from 15 mpg to 30 mpg around town. 

In reply to Toyman01 :

Fuel economy, as I’m sure you can attest is but one factor I’m taking into account. If it were purely an mpg battle I wouldn’t be looking at anything bigger than a 4cyl. 

So for sake of argument, let's say you switch vehicles. If you go from averaging 18mpg to 25mpg, how many weeks is that $20 savings at the pump going to take to payoff the higher mpg vehicle?

In reply to RevRico :

As I’m sure you've read above, I’m giving my truck to my son because he’s getting his drivers license soon. I’m not looking to buy a vehicle for the sole purpose of saving money on gas.

And a CV is only one of MANY cars I’m looking at as well. But in my research, I’m having a hard time explaining why these two vehicles are so close in mpg. 

Check http://www.fueleconomy.gov for the EPA  MPG rating that the manufaturers report on the Gov't test cycle. 

Check http://www.fuelly.com for mpg that actual owners report.  

In reply to ebonyandivory :

I somehow missed the part about it going to your son. That makes much more sense then. 

If budget allows, it might be worth taking a look at the newer, Taurus based, Ford Interceptor sedans. They've been selling for $3-6k at the PA state vehicle auctions. Awd, turbo charged, mid 20s mpg ratings, Damn near a sleeper.

In reply to John Welsh :

Thank you! Those places are where I’m getting my figures from. 

Using MPGbuddy, the figures are even closer.

In reality my 05 Avalanche 5.3 got 14.5 average unladen and my 99 p71 got right at 17, both in mixed driving.

In reply to ebonyandivory: Possibly I shouldn't write posts in the middle of the night!  Re-reading it now, it does sound ambiguous, which is not what I intended to convey at all.  Operating entirely without pesky facts, I originally speculated that the P71 would be in the 250 lb-ft at 4000 rpm range and the truck about 350 lb-ft at 3000, and I thought that a torquier engine working less hard (if it had six gears to help, instead of four) might use less fuel.  Then, when you supplied the relevant facts, all that speculation dissolved into dust.  So I have now arrived exactly where you started, wondering what gives.

In reply to Stealthtercel :

Awesome! I’ve been feeling dumb for being confused about the differences in vehicles combined with the similarities between mpg’s.

Don’t forget the truck fuel economy is for the engine and chassis combo. Different gear ratios will get different actual fuel economy results. Our crew can with pure gas can still knock down 23-24mpg highway. Putting around in E36 M3ty traffic I’m getting 17.5 on e10 winter fuel. One of my good friends had a civie cv and he averaged 16mpg. 

For whatever reason, it seems like some vehicles just get  unusually good or unusually bad mpg on the EPA tests, sometimes just due to the very specific test conditions, I think. 

As an example, my BMW is rated at 21 mpg on the highway (23 for a non-sport version with the taller diff).  In the real world, even at higher speeds than the EPA test, 25 mpg is realistic on the highway.  People with the taller diff report more like 27 - 28.