MPG still stinks! Help pls.
#12
09-07-2011, 10:57 AM
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#13
09-07-2011, 01:05 PM
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#14
09-07-2011, 04:56 PM
I said 12 mpg city and highway mixed, meaning i fill the tank up and do my usual driving , which is a combination of both city and highway driving. About 1/8 tank left, I refill it and check it by calculator. I dont pay any attention to the computer mpg, it always lies. It use to get 16 mpg w/mixed driving, but now its getting about 12. I run Shell 87 octane gas. Any ideas now?
AND I KNOW THE MANUAL SAYS 89 RECOMMENDED BUT 87 IS OK IF YOU DON'T GET PRE-DETENATION! But you can't hear a mild knock and over time it'll kill the engine. LOTS of warnings on this forum about continued use of 87 octane taking cylinders out.
It's just a bad idea to run 87 octane gas in an engine with a compression ratio of almost 10:1...
Replace it. It's a $35 part at the auto parts store and if the EGR is cruddy enough to generate a CEL, you usually only buy a month or two without it popping a CEL again by cleaning it...
Last edited by HammerZ71; 09-07-2011 at 05:01 PM.
#15
09-07-2011, 05:43 PM
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#18
09-08-2011, 10:27 AM
You're running 87 octane gas in a Hemi on a regular basis? Probably starting to have the long term effects of pre-detonation. Look for the dreaded cylinder misfire codes next, then it'll be new engine time!
AND I KNOW THE MANUAL SAYS 89 RECOMMENDED BUT 87 IS OK IF YOU DON'T GET PRE-DETENATION! But you can't hear a mild knock and over time it'll kill the engine. LOTS of warnings on this forum about continued use of 87 octane taking cylinders out.
It's just a bad idea to run 87 octane gas in an engine with a compression ratio of almost 10:1...
Replace it. It's a $35 part at the auto parts store and if the EGR is cruddy enough to generate a CEL, you usually only buy a month or two without it popping a CEL again by cleaning it...
AND I KNOW THE MANUAL SAYS 89 RECOMMENDED BUT 87 IS OK IF YOU DON'T GET PRE-DETENATION! But you can't hear a mild knock and over time it'll kill the engine. LOTS of warnings on this forum about continued use of 87 octane taking cylinders out.
It's just a bad idea to run 87 octane gas in an engine with a compression ratio of almost 10:1...
Replace it. It's a $35 part at the auto parts store and if the EGR is cruddy enough to generate a CEL, you usually only buy a month or two without it popping a CEL again by cleaning it...
#19
09-08-2011, 11:24 AM
Most just wait for it to generate a CEL. I see EGR CELs pop anytime after about 35k miles but some have gone 50k or more. I think a LOT depends on driving habits. I'm sure those who do the shorter, stop & go trips will see one fail sooner.
Since I use my Grand Cherokee as my daily driver (and because it's a 4x4 with front & rear lockers - I use it a good bit off-road too) I find myself only putting about 8k a year on my truck and it's mostly for trips up to the Georgia farm & back (about 360 miles each way), and only shorter runs while huntin' & stuff up there. So I replaced mine this past spring when I hit 50k. No CEL and it was actually in such good shape I cleaned it and put it in the box the new one came in as a spare.
Since the EGR can be a major contributor to gas mileage loss, I'd do it at 50k for the lousy $35 whether it generates a CEL by then or not.
The biggie is the TB, since the EGR dumps right behind the thing and the PCV dumps in the intake right in front of it, the TB tends to gum up pretty bad. I clean mine at 15k (which for me is about every two years) and would suggest 30k cleanings at worst. 15k if you're pulling, hauling or tend to take short trips...
Since I use my Grand Cherokee as my daily driver (and because it's a 4x4 with front & rear lockers - I use it a good bit off-road too) I find myself only putting about 8k a year on my truck and it's mostly for trips up to the Georgia farm & back (about 360 miles each way), and only shorter runs while huntin' & stuff up there. So I replaced mine this past spring when I hit 50k. No CEL and it was actually in such good shape I cleaned it and put it in the box the new one came in as a spare.
Since the EGR can be a major contributor to gas mileage loss, I'd do it at 50k for the lousy $35 whether it generates a CEL by then or not.
The biggie is the TB, since the EGR dumps right behind the thing and the PCV dumps in the intake right in front of it, the TB tends to gum up pretty bad. I clean mine at 15k (which for me is about every two years) and would suggest 30k cleanings at worst. 15k if you're pulling, hauling or tend to take short trips...