Impressed with increase in gas mileage with square body!

[chevymotocross]

Went from an average of 15 mpg mix driving to 18. Since I started taking college courses at local community college, relying only on my military reserve pay and money I had saved up, I changed my driving style.

305TBI which is in the best tune it can be in. Just recently rebuilt the TBI with a rebuild kit. Besides that, everything was already tuned up a few thousand miles ago (full ignition tune up, filters, etc). And yes, my speedometer gauge is correct!

Mods include:
dual exhaust (stock manifolds)
tbi spacer
pod spacer
k&n drop in
hypertech powerbowl
fuel pressure set to 13.5
Harrison TBI chip running hi-grade pump gas

Drivetrain:
3.08 gear
700r4 with vette servo
275/60/15 rear tires and 255/60/15 front set at 35psi all around
4/6 drop

Since I am trying to save as much $$$ I can while being a full time student before an upcoming deployment, I adjusted my driving style. I was never an aggressive driver but I was always over speed limit. On highway the speed limit here is anywhere from 50-65.... I always did 70-80. Backroads to school are 25-35 limits with no stop lights. I don't really do much "city" driving with lots of traffic and stop lights. It's back-roads and usually a highway trip.

Changes:
Highway: I keep it at 55-60. The truck is not dogging at all at those speeds even with the 3.08.

Backroads and in-town: Speed limit-5mph over. Easing up to traffic lights and sometimes timing them perfectly where I don't ever need to even hit the brakes. Pretending the gas pedal is an egg shell when taking off. Luckily, in town on take off, the 700r4 1st gear is great but the 3.08 shows it's badside on the 2nd gear upshift. Once I get up to cruise speeds, the 3.08 is fine. I think a 3.42 or possibly 3.73 would yield better mileage for my style.

Driving is also way more relaxing. I leave a bit early for where I am going. I find to be less stressed. I thought I would have issues with tailgaters and so far not bad. The highway really isn't an issue since all the speeders travel in the middle-left lane anyways. Back-roads and in town, traveling the speed limit sometimes gets an annoying tailgater but where I drive isn't too populated. I'm not one to brake check someone since that is equally as stupid. I just maintain my speed of at the actual speed-limit or 5 above.

18mpg is great for me. In fact, it's the best mileage I've gotten out of any of my past vehicles. My previous ranger v6 got 17. My current back-up vehicle, a 92 s10 blazer 4x4 4.3 TBI in good tune gets only 15 and WAY underpowered.

I was considering at one time of keeping my truck and getting a 2nd car. I realized that the cost of a car, the registration fees, insurance, and extra maintainence fees, don't justify the savings. For my driving, 18 mpg seems to be great.

I would love a 3.42 or 3.73 rear but it wouldn't be an update I would do in the near future.

Any other tips to maybe squeeze 20?

[875.3CHEVY]

no tips.nice truck btw

[Coffin Customs]

Leave your tailgate up if you don't already.
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[92GMCDriver]

what are you running for exhaust? after i got rid of the cat and put a single in dual out chambered muffler on my 92 i got about a 2 or 3 mpg increase. it may help in your case if you havent already done something like that.

[chevymotocross]

no cats, dual 2.25'' with thrush welded 2 chambers dumped before axle.

[thepenguin99]

nice truck. TBI V8 chevys always seem to get pretty good mileage compared to most other things, especially their 4.3 counterparts. I don't have any recommendations for better mileage. You mentioned high grade pump gas which I am assuming means premium. From a money saving standpoint it doesn't make sense for a low compression motor. I would go to regular.

[chevymotocross]

Only reason for the premium was because with the performance chip I was told it's a requirement. I may try mid-grade and see if there are any pinging issues and if not maybe drop down to low grade and try that. I didn't notice an extreme difference between this chip and the oem chip so it might be worthwhile going back to the OEM chip and running low grade fuel to really save.

[Corts60]

That is great mileage for a gas fed square body! Good job. I pull 18 in the city and 22 on the hwy, but I also have a non-turbo diesel and I drive the same as you do.

I think for a gasser you are doing great!

[Keith Seymore]

Nice truck, very nice stance.

Fold the mirrors in and see if you pick up anything....

(lol)

K

[Keith Seymore]

Sidebar: I am only halfway kidding about the mirrors.

In our wind tunnel testing, the base shape is usually pretty aerodynamic but when you start adding external protrusions (mirrors, door handles, flares, etc) each one is an incremental knock in the wrong direction. It all adds up.

Also - lowering a vehicle helps a lot, too, since that reduces the overall frontal area.

Lastly, slowing down is a huge help, since it is affected by the square of the velocity (its not just a linear relationship).

K

[bustedknuckles]

Very nice truck. Only thing I can think of that would help at all would be headers and electric fans.

[2badgn]

Nice truck! Can't tell by the pic, but do u have a Tonneau Cover?

This will help in the aerodynamics and also help to save some gas. U can buy all different types- soft, hard, roll up, hinged, etc. They are also available in over the rail or not over the rail. I went with a Truxedo. It was $500 but it has a lifetime warranty, makes the truck look better and u can store things and keep them dry when it rains /snows.

There are cheaper ones but u get what u pay for.

[Hotrodrobert]

Buy and learn to use a vacuum guage. You will probably be surprised how often you cause the vac to drop into poor economy. You may find the engine is happier with the trans in 3rd instead of 4th gear at lower speeds.
You can also try changing the initial timing by moving it +/- 2* at a time and driving the truck. DON'T LET IT DETONATE OR SPARK KNOCK!! you can probably run 87 if you do.
Doug Roe wrote a book about fuel economy that was very good. He won several national fuel economy competitions a few years ago with cars that weren't supposed to get mileage.
An exhaust crossover or, better, an X pipe will also help.
Also, heat is the enemy of power, but the friend of economy! Be sure your warmup systems are working properly, your thermostat is FACTORY, not cooler, like a 180 or something. Again, lower temp is more power, less economy!!
Electric cooling fans help a little but not a lot and you can buy a lot of fuel for what they cost.
Did some testing with headers and trucks about 2000-2002 and found Tri-Y headers like Doug Thorley were a real help and no other, not even the best full length headers could compare.
I have seen MANY TBIs with atomization problems no one knew they had. Take a timing light and hook it up as usual then use it to look at the spray pattern of the injectors. If you can see droplets or a stream, you have gas sucking dirty injectors!

[Pork Chop]

Originally Posted by chevymotocross

Went from an average of 15 mpg mix driving to 18. Since I started taking college courses at local community college, relying only on my military reserve pay and money I had saved up, I changed my driving style.

305TBI which is in the best tune it can be in. Just recently rebuilt the TBI with a rebuild kit. Besides that, everything was already tuned up a few thousand miles ago (full ignition tune up, filters, etc). And yes, my speedometer gauge is correct!

Mods include:
dual exhaust (stock manifolds)
tbi spacer
pod spacer
k&n drop in
hypertech powerbowl
fuel pressure set to 13.5
Harrison TBI chip running hi-grade pump gas

Drivetrain:
3.08 gear
700r4 with vette servo
275/60/15 rear tires and 255/60/15 front set at 35psi all around
4/6 drop

Since I am trying to save as much $$$ I can while being a full time student before an upcoming deployment, I adjusted my driving style. I was never an aggressive driver but I was always over speed limit. On highway the speed limit here is anywhere from 50-65.... I always did 70-80. Backroads to school are 25-35 limits with no stop lights. I don't really do much "city" driving with lots of traffic and stop lights. It's back-roads and usually a highway trip.

Changes:
Highway: I keep it at 55-60. The truck is not dogging at all at those speeds even with the 3.08.

Backroads and in-town: Speed limit-5mph over. Easing up to traffic lights and sometimes timing them perfectly where I don't ever need to even hit the brakes. Pretending the gas pedal is an egg shell when taking off. Luckily, in town on take off, the 700r4 1st gear is great but the 3.08 shows it's badside on the 2nd gear upshift. Once I get up to cruise speeds, the 3.08 is fine. I think a 3.42 or possibly 3.73 would yield better mileage for my style.

Driving is also way more relaxing. I leave a bit early for where I am going. I find to be less stressed. I thought I would have issues with tailgaters and so far not bad. The highway really isn't an issue since all the speeders travel in the middle-left lane anyways. Back-roads and in town, traveling the speed limit sometimes gets an annoying tailgater but where I drive isn't too populated. I'm not one to brake check someone since that is equally as stupid. I just maintain my speed of at the actual speed-limit or 5 above.

18mpg is great for me. In fact, it's the best mileage I've gotten out of any of my past vehicles. My previous ranger v6 got 17. My current back-up vehicle, a 92 s10 blazer 4x4 4.3 TBI in good tune gets only 15 and WAY underpowered.

I was considering at one time of keeping my truck and getting a 2nd car. I realized that the cost of a car, the registration fees, insurance, and extra maintainence fees, don't justify the savings. For my driving, 18 mpg seems to be great.

I would love a 3.42 or 3.73 rear but it wouldn't be an update I would do in the near future.

Any other tips to maybe squeeze 20?

Posted via Mobile Device

[grs]

I was getting 19 mpg on the freeway. I replaced the bad egr valve and the mpg went up to 24. I have a 305 engine with a 700R4, and TBI. Check your mpg on the freeway. Not stop and go freeway driving. Let us know what you get.

[Pork Chop]

Very nice, thinking about a 4/6 drop when I'm finished with body and paint
Posted via Mobile Device

[john_p]

great looking truck.. myth busters seem to prove the tail gate thing to be a non factor, i don't know.. i am a big fan of the vacuum guage as well, learn to keep one of those in the green, it helps.. good post and thanks for your service.. i was last deployed back in the late 60's but some things don't change.

[chevymotocross]

Thanks everyone!

2badgn, forgot to mention that. After deployment, a cover will be the first thing I get for the truck! Also, beautiful looking truck! I remember seeing a thread with some more pics of yours, I love the factory look of your rig!

Another thing I forgot to mention. The EGR system. I currently have it blocked off. I replaced the OEM gummed up EGR a few years back. I wrote the factory EGR numbers on the new EGR, but I remember there was no P or N at the end of the numbers to represent positive or negative backpressure type. After removing the cats and dumping the exhaust, I was getting code 32 on the freeway. Also, my truck was stalling occasionally after highway use at the exit ramps. I don't think the EGR was closing properly causing a vacuum leak. Come to find out, the replacement egr says POS on it. I believe I need a NEG backpressure EGR especially since I have no cats and the exhaust is dumped.

Since I plugged the current EGR, there is no more stalling but a properly working system will probably yield better mileage.

[turbo350]

Originally Posted by chevymotocross

Thanks everyone!

2badgn, forgot to mention that. After deployment, a cover will be the first thing I get for the truck! Also, beautiful looking truck! I remember seeing a thread with some more pics of yours, I love the factory look of your rig!

Another thing I forgot to mention. The EGR system. I currently have it blocked off. I replaced the OEM gummed up EGR a few years back. I wrote the factory EGR numbers on the new EGR, but I remember there was no P or N at the end of the numbers to represent positive or negative backpressure type. After removing the cats and dumping the exhaust, I was getting code 32 on the freeway. Also, my truck was stalling occasionally after highway use at the exit ramps. I don't think the EGR was closing properly causing a vacuum leak. Come to find out, the replacement egr says POS on it. I believe I need a NEG backpressure EGR especially since I have no cats and the exhaust is dumped.

Since I plugged the current EGR, there is no more stalling but a properly working system will probably yield better mileage.

Sweet rig!

I had an '87 350 tbi in a 3/4 ton conversion van. Best that van ever saw was 12, maybe 13 mpg even when it was new. Had 700r4 and 3.08 rear and of course the heft and bulk of the van. Using that for a very loose comparison I'd say you are doing a heck of a job and squeezing out the max amount of economy out of what you have.

[pig rig]

Ive got an 88 with the 454 tbi in it Ive done a lot to get more power out of it and in the process of that I went from around 10 mpg to 12 mpg then we took atrip to socal in it and on the way home the clutch fan went out so I pulled it off and for the last 600+ miles I got just short of 16mpg out of it.
so I put electric fans and I did some reading on the advantages to running an MSD 6al spark box so I added a 6al and an MSD distributor and new injectors
but Ive developed engine problems and I still havent been able to do a few hundred mile road trip to see if its improved.

[bustedknuckles]

Blocking the egr system is definitely better for your mileage.

[INSIDIOUS '86]

headers are a great improvement, if your budget allows go for try-y's for sure stay with the performance chip, it prob has a better fuel curve otherwise i say it looks like things are doin great i would say an aftermarket intake that flows easier especialy at low speeds will increase eficiancy we feel this as an hp increase as well, porting the cylinder heads and making better fow charecteristics helps too

anything that makes it easier for the engine to produce more power with the same amount of fuel is a good thing

more torque means you move farther/faster with less effort

[franky69c10]

Originally Posted by bustedknuckles

Blocking the egr system is definitely better for your mileage.

i have a stock 87 350 tbi it does lag when i press the gas how do i go about blocking the EGR system and when i do will i throw any codes, is good to block the EGR system
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[coater]

Chevymotocross, Great looking truck!!! Do you have anymore pictures of it? Would you be willing to give me some info on the size of wheels and tires? Love the stance!!

[chevymotocross]

Originally Posted by coater

Chevymotocross, Great looking truck!!! Do you have anymore pictures of it? Would you be willing to give me some info on the size of wheels and tires? Love the stance!!

How my plugs look:

The wheels are 15x8 rallies. 275/60 rear and 255/60 front. Trim rings and center caps came off a chevy fullsize 80s van.