Hoping for some insight here from all the experience on the forum. 1200 miles ago I installed a TxC CAI kit on my truck as well as a new OEM GM air filter. Other mods to the truck are shown in my sig.

Previous to this I was averaging 16.34 mpg hand calc, empty. I was anticipating a bump in MPG with this mod, and so far I am sorely disappointed. Since the install I have averaged 14.97 mpg unloaded. My towing mileage has not changed appreciably.

I just changed the diffs and tranfer case recently - all synth fluids. My driving habits are the same, generally not on it very hard. I think my trips might be shorter on average which I know affects mileage. The only other thing I know is different is that the station where I buy most all of my fuel recently changed to 6-20% biodiesel. I know there is less energy content in the bio fuel, but I think something else must be going on.

I bought the truck with 34,500 miles, now has 39,200, and I have not changed the fuel filter. Can a restricted fuel filter hurt MPG?

Could I have installed the CAI kit wrong?? It looks like I got it right according to the pictures.

When do they change to winter fuel and how much MPG drop can you expect from that?

I dunno what else to think at this point. Thanks for any help. Sure appreciate it. :)

What are you getting now for MPG? I am also getting 16-16.4 MPG...

Currently about 15. I dropped about what I was hoping to get as an increase - about 1 or so mpg.

If you did the bio change at the same time it will be impossible to gauge. Go back to dino so your comparing apples to apples.

And change the fuel filter, that's cheap insurance.

If you did the bio change at the same time it will be impossible to gauge. Go back to dino so your comparing apples to apples.
To clarify, I didn't really "do" any bio changes, but my fuel station started carrying bio blend fuel. I'll look for some conventional fuel, but I figure there has to be some experience out there that can tell me if a bio blend fuel can have a 8+ % negative effect on my fuel economy. Can anyone comment?

change the fuel filter!

ive seen a 2 mpg drop once they change to winter blend:mad:.bastards.:mad:
try using regular diesel and see if there is a change.also change fuel filter its possible the bio blend loosened some crap up and clogged the fuel filter.

ive seen a 2 mpg drop once they change to winter blend:mad:.bastards.:mad:
try using regular diesel and see if there is a change.also change fuel filter its possible the bio blend loosened some crap up and clogged the fuel filter.


You wouldn't think bastards if you were stranded along side the road with a gelled up truck.

Make sure you put in the D-Max air filter. They are different than the gas engine filter.

Change the fuel filter as others have said. We have seen with farm equipment where the biodiesel breaks loose crud built up in the tank and plugs up fuel filters. It seems unlikely that this would be the case with only 38k miles on your truck.....But it could be crud in the storage tanks from where you get your fuel that has been broke loose.

Change the fuel filter as others have said. We have seen with farm equipment where the biodiesel breaks loose crud built up in the tank and plugs up fuel filters. It seems unlikely that this would be the case with only 38k miles on your truck.....But it could be crud in the storage tanks from where you get your fuel that has been broke loose.

X2! Restriction in the fuel filter can have a big impact on MPG!

You got two things going here: bio and winter blend. Both have lower heat value than convention diesel. I typically lose 1.5mpg to winter blend.

Moved to the Air Intake Upgrade section! ;)

Bio diesel has less thermal energy for the same volume as normal #2, so you will be using more of it to do the samework. In other words, automatic drop in mileage. It must be cheaper to be worth it.

Same thing applies to E85 versus regular gas, it has less energy, so mileage falls. But its cheaper too.

So far there is no win win for the consumer. :(

Bio diesel has less thermal energy for the same volume as normal #2, so you will be using more of it to do the samework. In other words, automatic drop in mileage. It must be cheaper to be worth it.

Same thing applies to E85 versus regular gas, it has less energy, so mileage falls. But its cheaper too.

So far there is no win win for the consumer. :(

Understood. My question is what is the reduction in energy for a 6% bio blend, or what is the impact on mileage people have been seeing? I don't have enough info to determine if it is just the fuel or I have something else going on. I am trying to fill with non bio to see if my mileage goes back up but I don't have enough data yet. Thanks!!

Very much of a restriction in the filter will cause a hard or no start condition. Ditto what SLT said. Later! Frank

Bio diesel has less thermal energy for the same volume as normal #2, so you will be using more of it to do the samework. In other words, automatic drop in mileage. It must be cheaper to be worth it.

Same thing applies to E85 versus regular gas, it has less energy, so mileage falls. But its cheaper too.

So far there is no win win for the consumer. :(

Thats not true :Nonono: All the ricers are burning E85 now because they are getting more power and more boost out of it. I agree with bio though, that stuff is no good

e85 does burn faster in vehicles you do see a milage drop.but it has a very high octane rating that works great for race applications.

Thats not true :Nonono: All the ricers are burning E85 now because they are getting more power and more boost out of it. I agree with bio though, that stuff is no good

Actually it is true, E85 has approximately 82,000Btu whereas gasoline has approximately 110,000Btu.


Where the ricers are getting the power is from the octane rating of E85 which at 100-105(ish) is higher than gasoline at 85-93 allowing them to run either higher compression or additional boost.


So a normal grocery getter will get roughly 20-25%% worse fuel mileage with E85, similar to how unless you're tuned for it BioDiesel will result in an approximate 8%-10% reduction in fuel mileage.

For the OP, last year running home brew B100 I dropped 2mpg on average, when I was running commercial B20 prior to that the difference was perhaps .5mpg if that. B5-B20 (depending on quality) doesn't have a huge impact on mpg from my experience. It will however as noted clean your fuel system, rather quickly as well, good bet would be to change your fuel filter a couple of times over the next few thousand miles. You'll likely be surprised at how much gunk is in your fuel system even at 30-50k miles.