Ive been trying to figure out ways to improve my MPG...

Ive got a 99 Blazer 4x4 4 door LS with 235,000 on the original motor and transmission. I've recently checked and got 12.6mpg City and 15.8 Highway which is unacceptable to me given the amount of money I've put into my Blazer in the past couple years to keep it running like new. And I literally mean like new. This baby purrs like a kitten and runs flawlessly...in the past 2 years Ive done the following...
-Fuel injection system
-Plugs 2x
-Wires2x
-Distributor +Cap +Rotor
-MAF Sensor
-MAP Sensor
-Crankshaft Sensor
-Ignition Module
-Fuel Filter
-Fuel Pump
-Air Filter
-New CAT was put on 3 years ago
-Replaced rear diff gear oil last week with fresh Synthetic Valvoline

Basically everything Tune up realated has been done
The only issues my Blazer has is a small Timing seal leak that its had for years. Nothing major and I always keep extra oil with me and keep it topped off. It leaks maybe a 1/2 quart every 2 weeks, sometimes a month. I use Valvoline Full Synthetic oil, always and fuel injector cleaner every 3 fills... I plan to fix the timing seal leak and do a Timing Chain while im at it within the next 6 months

I do have a damaged exhaust pipe that I know is restricting flow a little but only causes noticieble problems when im gunning it up a steep hill on the highway but I have a new pipe and plan on installing it today to fix that. I also have a new K&N filter at home that just got delivered today that I will be putting on.

The only thing about my Blazer I can say probably hurts the mileage is my 30" Cooper Discoverer STT tires but other than that everything mechanically is great. I keep them around 35psi and got an alignment last month when I lifted it 1.5" with Shackles and torsion crank

Other than replacing my squished Y Pipe today and my K&N filter I also plan to drop the mechanically cooling fan to free up the horsepower it uses to run and Im going to install TWO 10" electric fans.
What else can I do to help MPG?

 

Wow, lotta stuff, and most of it could adversely affect fuel mileage if not done properly using the right parts and procedures. Distributor cap, rotor, fuel pump, & spark plugs: did you use AC Delco? It does make a difference. Have you checked camshaft retard, fuel pressure and leakdown? If so, what were the readings? Did you perform the crankshaft position sensor relearn after replacing the sensor? It is mandatory. Torsion bar crank is definitely a problem if chassis ride height is out of spec. It will cause the CV joints to bind. Bigger tires will reduce mpg due to more drag. K&N air filter will raise havock with the MAF sensor and kill mpg too. The list goes on, but there are some things to start with.

 

Why would the k&n cause problems? I use OE parts all the time on it. My dad helped me with the crank sensor and I remember him doing the relearn procedure but when it comes to the retard I'm not sure. That's a language I don't speak. My dads been a mechanic for 30+ years so I'm confident in his ability to do it all right. He also helped me with most of the work on all these parts

 

The oil used on the K&N filters coats the MAF sensor elements which causes skewed frequency readings to be sent to the PCM. Often without setting any DTC's, but causing engine performance issues related to the air fuel mixture. A good quality, name brand air filter, (AC Delco, Purolator, Wix, Hastings, etc) will do just fine, without the problems, and save you money, it's a no brainer

 

The things that you have done to your running gear IE raised up and big tires, are in opposition to fuel efficiency. Either eat your cake or put it back in the refrigerator. Lower your chassis and put small hard tires on then state that your milage is unacceptable. Until you do that your milage is acceptable, is it not?

 

This!

 

Monitor engine vacuum and drive to keep that as high as possible.

City you get what you get with a 4000+ pound lifted vehicle with big tires. Only thing you can do is keep your foot out of it and A/C off. Easy starts - don't ride people's asses - relax.



Highway,

• Make sure TCC is engaging at speeds above 45mph (worth about 2-3mpg)
• Keep the speed below 60mph (you are pushing a big tall brick through the air). You don't have to drive the speed limit.
• Keep your foot out of it.
• Turn off the A/C

You might be surprised what a Blazer will get at 55mph steady level road with the A/C off. Once you know what it can get, you can drive accordingly without complaint.

FYI my stock 2001 LT runs 2000RPM at 70MPH in with stock size tires in OD with TCC engaged. Only 1280RPM at 45MPH. Your bigger diameter tires would only throw your speedo off 3.5%, but the wide tread would be more resistant to rolling and speed changes. Those little 4.3's don't have much power when lugging, and you may be having to get into the throttle more than usual as a result just to maintain. You can do the 55mph steady drive above to establish a baseline.

Mine got best of 23 mpg over 60 miles that were steady and very carefully driven at 55-60MPH. Been getting 19mpg with A/C on through rolling Interstate highway at 65mph. Bump it to 70mph and I get 16MPG. 75mph and I get 14MPG. Never got better than 14MPG in city - usually 13 in city.

Good luck