Increasing Fuel Mileage - Worth The Money?

[strousek]

I have two older trucks that I am the only owner of and both are recently experiencing some pretty good drops in their effective fuel mileage. One is a 2015 Duramax that used to get anywhere from 18 to 20 for me. Now with a little over 190k miles she regularly gets 14 or 15 MPG. I live in CO so emissions are not easy, but there are ways to get around it. Best solution to increase the fuel mileage would be to do the DEF delete however I have a hard time spending $4k-5k to perform the complete delete and exhaust improvement to save a little money on diesel. Doesn't seem like the investment to return ration makes much sense there.

My second truck is a 2005 Chevy 5.3L that when new she purred along at 18 MPG. Again this truck now with 160k on it will only get 14 MPG.

I keep the tires rotated and inflated properly, all joints greased and clean air filters. Does anyone have any other tips to increasing fuel mileage that doesn't cost twice the amount of just filling the tank more often?

 

[MallardSX2]

I gave my Cummins a historectomy at 75,000 miles. I went from 16 to 20 on the highway.
I figured I needed to get 50,000 miles to break even based on no DPF costs and increase in MPG.
I broke even at 125,000 miles and put another 115,000 miles on it and it is still running strong at 240,000 miles....Still running ORIGIONAL BRAKES AND ROTORS with lots left.....Still a great running truck. It was 100% worth it for me.

Truck is for sale BTW. First one to GA with 20K cash takes it home.

 

[svivian]

Your truck will last longer without the emissions which was more of a reason I freed my ford of them when i bought it.

 

[fmyth]

I have two older trucks that I am the only owner of and both are recently experiencing some pretty good drops in their effective fuel mileage. One is a 2015 Duramax that used to get anywhere from 18 to 20 for me. Now with a little over 190k miles she regularly gets 14 or 15 MPG. I live in CO so emissions are not easy, but there are ways to get around it. Best solution to increase the fuel mileage would be to do the DEF delete however I have a hard time spending $4k-5k to perform the complete delete and exhaust improvement to save a little money on diesel. Doesn't seem like the investment to return ration makes much sense there.

My second truck is a 2005 Chevy 5.3L that when new she purred along at 18 MPG. Again this truck now with 160k on it will only get 14 MPG.

I keep the tires rotated and inflated properly, all joints greased and clean air filters. Does anyone have any other tips to increasing fuel mileage that doesn't cost twice the amount of just filling the tank more often?

2005 Chev with 5.3:
I'd get a OBD2 tester and pull the codes and address. You can buy a code reader for not much $ or have them read at a parts store. Then clean the injectors. It's quite possible they are really dirty/partially plugged or failing to close completely after spraying. Don't know if there's a place where you can get them cleaned and serviced near you but they are several companies that you can ship them to. It's easy to pull them. You could also order caps/screens and o rings online and use a Harbor Freight sonic cleaner to do it yourself. You can find a video on how to do it on youtube. I'd also replace the PCV. With that many miles you are also likely getting some blow by oil vapor back into your intake which will not help your mpg. Easy solution is to install an oil catch can. I'd also replace the coil packs, spark plug wires and spark plugs. While the plugs are out use a borescope to look at the tops of the pistons to see if there is a lot of carbon on top. Hopefully they all look the same. If they are all dark except one or two that would indicate an injector hanging or leaking down or a potential HG leaking cooling into that chamber. I'd do a compression test and a leak down test. You can probably rent/borrow the testers from a auto parts store. Lastly I'd pull the catalytic converter and inspect it. If it's significantly plugged it should throw a code but not always. If so replace it.

 

[strousek]

2005 Chev with 5.3:
I'd get a OBD2 tester and pull the codes and address. You can buy a code reader for not much $ or have them read at a parts store. Then clean the injectors. It's quite possible they are really dirty/partially plugged or failing to close completely after spraying. Don't know if there's a place where you can get them cleaned and serviced near you but they are several companies that you can ship them to. It's easy to pull them. You could also order caps/screens and o rings online and use a Harbor Freight sonic cleaner to do it yourself. You can find a video on how to do it on youtube. I'd also replace the PCV. With that many miles you are also likely getting some blow by oil vapor back into your intake which will not help your mpg. Easy solution is to install an oil catch can. I'd also replace the coil packs, spark plug wires and spark plugs. While the plugs are out use a borescope to look at the tops of the pistons to see if there is a lot of carbon on top. Hopefully they all look the same. If they are all dark except one or two that would indicate an injector hanging or leaking down or a potential HG leaking cooling into that chamber. I'd do a compression test and a leak down test. You can probably rent/borrow the testers from a auto parts store. Lastly I'd pull the catalytic converter and inspect it. If it's significantly plugged it should throw a code but not always. If so replace it.

Very much appreciate all the input. I have an OBD2 reader and no current codes. Only issue I have is I put on an aftermarket exhaust years ago on the truck. For whatever reason I go through an 02 sensor now about once every 2 years. My local shop said its because of the after market muffler not giving the same flow and pressure as a stock exhaust. Change the sensor and it clears the code but never changes MPG.

I will for sure look into the other issues here. She burns a half quart of oil per change so that makes sense on the intake vapor. Thank you for the advice.

 

[Steve300xcw]

I dont see many freeway miles, and I'm a lil aggressive with the throttle so my views might be a bit skewed. But mid teens in a full size rig doesnt sound bad

 

[fmyth]

Very much appreciate all the input. I have an OBD2 reader and no current codes. Only issue I have is I put on an aftermarket exhaust years ago on the truck. For whatever reason I go through an 02 sensor now about once every 2 years. My local shop said its because of the after market muffler not giving the same flow and pressure as a stock exhaust. Change the sensor and it clears the code but never changes MPG.

I will for sure look into the other issues here. She burns a half quart of oil per change so that makes sense on the intake vapor. Thank you for the advice.

Good luck. Will be interested to hear if you are able to get the mpg's back up.

 

[JRMiller]

There are a myriad of reasons an older vehicle will lose efficiency, but the most cost effective way to seek improvement is cleaning the fuel injectors. The gradually lose their spray pattern due to deposits and therefore don't atomize the fuel small enough to make a good air/fuel ratio mix. The most potent in-tank additive you can buy to clean them is called BG 44k. Dealers have it but some parts shops have it as well. Its pricy (about $25 a can) compared to typical ones found at auto parts stores, but it is much, much more effective. I usually put one in my tank every three months. You can also perform a direct clean via the injector rails which is faster and even more effective, but it requires specific equipment, tools, and knowhow.