A fickle beast it can be......

[Hedgehog]

First Of I want it understood that I'm not complaining. I'm not really even looking for answers. We are just talkin' here, passing the time.

I have mentioned many times that I'd like to get better mileage from my Jeep, not crazy better mileage just some more 15 or 16 mpg would be nice. Make no mistake my Jeep has instrumentation problems, the speed ometer has been a small problem, but the odometer seems to be more or less spot on. To get past this with a desire to get accurate data my speed and mileage information comes from my automotive Garmin Nuvi GPS. Ever since the Jeep hit the road, about 1,200 miles ago now we have kept track of every mile driven. Yes, there has been some mistakes and that data was discardedd. Anyways data is as accurate as I can get.

The first few weeks the CJ was pulling in a gastly 8.5-9 mpg. After some clean up of minor but smelly leaks we were up to 10mpg. Then one tank pulled in 12 mpg, but in reality she settled down to ~10.5. LAst week while on here I realized that everything that could be changed had been, except for the air filter. This one came on the engine I replaced. Sure I used the air compressor to blow it out, but the old thing was far over due for a change.

I like K&N Air filters. Naturally Autozone had to get one from their warehouse, a next day delivery. It was ordered. But I can't leave anything alone so the filter I had was cleaned then blown dry. The next day the Jeep pulled in 13.8 mpg. This came after a smart alik in a small engine european sports car thought he'd show me and the kid in me stepped up to the plate, Little screaming sports car against a big American V8. He made a lot and I mean a lot of noise, the 360 did a Jeeps impression of sucking his head lights out of his grill. Oh my goodness even after being stupid, 13.8 MPG, I was very pleased.

THe new K&N came in and I expected great things from it. But but but the next tank full dropped down to 9.5 mpg. WHAT!

Over the week end we got 10.4, then OMG a nice 12.6 and a 13.4. Some driving was 4 wheeling expecting the worst, nope we got 12.6, on the highway and around shopping 10.4. Screaming down the highway and 4 wheeling 13.4.

I think this is going to be a vehicle that is finicky about the type of gas used in it. That is ws about the only major variable, besides 4 wheeling that is.

 

[hdgapeach]

THe new K&N came in and I expected great things from it. But but but the next tank full dropped down to 9.5 mpg. WHAT!

Right there with you on the K&N filter. Figured out the hard way on my H-D. The filter is just one of many steps to making improvements. Along with the filter that helps breathing in, you then have to make it breath out to match. Once the "breathing" is taken care of, then the carb jetting adjustments begin. After that, I had to get the right temp. plugs and tinker with the gapping.

The air filter alone reduced my mileage 8 mpg. Blew my mind to say the least.

 

[Hedgehog]

I've been running K&N air filters on most all my vehicles since the early '80s. Like'em a lot. They are getting expensive, but isn't everything these days. The next engine maintenance thing will be to have my 2150 rebuilt. Yes, I know I can do it myself, but automotive carbs scare me to death.

I'm getting the impression that this engine doesn't mind some horsing around, but a steady drive around 70 mph sucks up fuel like a sponge.

 

[HackFabrication]

I have pretty low mpg expectations for my CJ5 :



4.56 gears, T-18 , and 32" tires. At 70 mph my Ford 5.0L will be screaming at 3352 rpms. At 55 it's 2633 rpms. At 45 it's 2155 rpms. And probably a bit higher across the board, as most tires don't measure what they claim. I won't know the actual mileage until it gets on the road later this summer. But I'm really hoping it's in the 10-12 range. And this engine has to burn premium 91-93 octane.

By comparison, my 2014 Grand Cherokee with the 5.7L Hemi and 8 speed automatic, is around 1800-1900 rpms doing 70 mph. And averaging 23-25 mpg (using the onboard computer) at that speed. Although 89 octane is recommended by Jeep, it can burn the cheaper 87 octane.

 

[hdgapeach]

I've been running K&N air filters on most all my vehicles since the early '80s. Like'em a lot. They are getting expensive, but isn't everything these days. The next engine maintenance thing will be to have my 2150 rebuilt. Yes, I know I can do it myself, but automotive carbs scare me to death.

I'm getting the impression that this engine doesn't mind some horsing around, but a steady drive around 70 mph sucks up fuel like a sponge.

The expense is really what turned me off on the K&N. The filter cost would be tolerable if I didn't have to spend so much to compensate for the filter installation. And that "cost" includes the extra dollars spent on fuel while I'm getting less mpg! That ain't cheap no more!!

 

[Hedgehog]

Hack - Well yeah, your expectation is far different from mine. Yours certainly is pretty. While mine isn't stock it also isn't an experiment into "what can be done". If I were a little more into this I'd drive the highway at 55 for 50 miles and check the mileage, then 60, then 65, then 70. I bet real data would be there somewhere.

hdgapeach - One thing about the K&N, if taken care of they last forever. I occasionally get a gas smell from somewhere and the jeep pops on deceleration indicating to much gas floating around. Rebuilding the carb. might bring a happy surprise or two. God only knows what the engine PO did with this engine. I know it was rebuilt and it starts and runs strong. That's about all.

The Jeep came with a new exhaust, headers, magna flow mufflers and cats. I can't really open her up much more than she already is.

 

[DHugg]

I had (briefly) a 454 V8 in a Grand Marquis Mercury that got 16MPG...... 8 on the road and 8 in town. But I do get better mileage from Ethanol-free. It is more expensive, doesn't make up for the cost in mileage gain, but I hope long-term I have less repairs to make.

I'm getting 10 with my AMC 304 1980 CA smog-system-gelded engine. One of the reasons was that the last distributor-reworker left the key out of the reluctor keyway on the shaft, and no good can come of that. The other discovery was that someone had plugged the vacuum advance tube with a bearing.

Now I'm beginning an ignition upgrade to MSD-6A. I expect better results from better spark. But the battle never ends between Jeep working Cheap, and me trying to gold-plate everything so that I don't have to rework what I do.

 

[Old Dog]

Hack - If I were a little more into this I'd drive the highway at 55 for 50 miles and check the mileage, then 60, then 65, then 70. I bet real data would be there somewhere..

You might be surprised at the results. Driving a brick through the air at 70 takes a lot of energy.
When I tow my jeep I can get 2-3 more mpg from my truck by going 60 instead of the 70 speed limit.

 

[Neuner]

I like this thread. Hope it doesn't get off topic.

As more of an add to the 'fickle' comment, I've experienced the same with my AMC 258 i6 / 4.2l . I track every mile and gas input with GPS as well and chart it out. I average 15.5mpg but it does not take much to get off course. I even fill up at the same gas station at the same pump. Seems like I'm in constant tuning mode to keep it where it is. So far it seems like I've been doing it long enough to be able to tell if it's bad gas, dirty filter, etc event so it doesn't take long to identify the problem. I make one change at a time and watch the result.

 

[Hedgehog]

After tackling the really big stuff with my CJ, it's down to refinement. When I got the new engine, from a '82 wagoneer it had the stock wagoneer filter housing witht he big unfinished square intake. The Wagoneer intake had an intake in the grill with a hose going to the filter. It makes sense to bring cooler air into the carbrorator. In my desire to make it look stock I replaced the hose fed, without the hose, housing with a stock '75 filter housing. The stock '75 one has a nicely finished horn affair, all in all a small intake designed to create a ventury effect to draw off gasses from the charcoal filter. I'm thinking about replacing the '75 with the '82. Bigger intake, more air, HUGE increase in gas mileage, we are talking in the 20 to 30 mpg range ..... okay there is no seriousness in the last mileage guess, but it might make a difference, who knows.

 

[Hedgehog]

This evening I pulled the '75 air filter housing and put the '82 housing on. The last time I worked on the timing I decided to use a different vacuum port that didn't rely on the old emissions components. The Jeep didn't respond well to that, am suspicious that there wasn't enough vacuum on that port. So I switched it to a post I knew was working properly. Darn, what a difference. The idle speed went from ~600 to ~900 and slow speed response will set you back in your seat in a serious way.

Tomorrow I'll recheck timing and adjust the idle speed back down where it belongs. Now I'm itching to see what the next fill up shows.