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GAS MILEAGE


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1dodge1mopar
User

Dec 8, 2014, 4:42 PM

Post #1 of 11 (991 views)
GAS MILEAGE Sign In

I recently blew an engine-'01 CHEV SILVERADO 5.3L-& had an '02 5.3L transplanted. I was getting 16-17 mpg with the original. I checked the gas mileage on this engine after fill up & discovered it was only 9.9 mpg. the engine was purchased from a state renoun salvage co.=CARNEY'S AUTO SALVAGE-AMES, IOWA. I was told the engine had 140k on it. it cost me $600. the people that I had put it in said it was the "SOUNDEST" engine they had ever changed. the owner told me "you have a "REAL SOUND" engine.
what I would like to know if the poor mpg is from not being compatible with the ECM that is presently in it. this is the only reason I can possibly think of. the only other change that I should note-that might be relavent-is that the replacement engine's manifold was changed to the original VORTEC style manifold.
could this manifold change had an affect on mpg?? or is it the ECM compatibility??


thanx


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 8, 2014, 5:08 PM

Post #2 of 11 (981 views)
Re: GAS MILEAGE Sign In

What happened to the original engine?



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Discretesignals
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Discretesignals profile image

Dec 8, 2014, 5:38 PM

Post #3 of 11 (977 views)
Re: GAS MILEAGE Sign In

There really shouldn't be any difference between the 01 and 02 engines. Don't know what you mean by Vortec intake because the intakes are the same for both years.

Check engine light on?





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1dodge1mopar
User

Dec 8, 2014, 8:17 PM

Post #4 of 11 (950 views)
Re: GAS MILEAGE Sign In

the bad engine was returned to the salvage co. for core deposit.


1dodge1mopar
User

Dec 8, 2014, 8:27 PM

Post #5 of 11 (946 views)
Re: GAS MILEAGE Sign In

when I went to CARNEY'S SALVAGE in AMES, IOWA, TONY told me that "MY" intake manifold would have to be taken off to replace the one on the engine I was buying because of the ECM set up with my manifold. I personally am not knowledgeable of the "manifold" interaction with the ECM of the different engines. from what he told me, in the way he told me-without hesitation, I accepted it as "GOSPEL" & had it done on the transplant.
is it an engine incompatibility or ECM not recognizing the set-up?? when a different engine is replaced, should the ECM card also be replaced or is there way to alter the compatibility issue-if there is one. I'm on a limited SS budget. I had to get my landlord to defer last month's rent of $750 to pay for installation of $1012.
I need some info on what to do to at least get the mpg up to around 14-15mpg.
thanx


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 9, 2014, 2:55 AM

Post #6 of 11 (925 views)
Re: GAS MILEAGE Sign In


Quote
the bad engine was returned to the salvage co. for core deposit.


LOL.... That's not what i meant. In what way did the prior engine fail?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 9, 2014, 4:38 AM

Post #7 of 11 (922 views)
Re: GAS MILEAGE Sign In

1dodge1mopar: This issue of MPG is so variable on anything it's tough to nail down on anything. It's colder, fuel formulas change for Winter use and plain cold vehicles don't roll as easily so take more energy all against you for MPG at a time when an engine apparently blew up bad enough to need another EVER SO PERFECT used engine as TONY said he's ever seen! Only 140,000 miles! Oh my!


You have to compare real MPG with the exact same conditions over a couple tanks of fuel or more. How many times have you recorded this new MPG since the last engine? Same everything or #s get messed up easily.


Anyone wants the most MPG they can get. I would think if this is wasting fuel that much it would be setting off all kinds of codes and not running very well.


I'm not sure yet observations are accurate if this all just recently done and if anything is truly wrong.


Not a mechanical point but if MPG matters that much to you why are you driving a full size truck at all?


T



1dodge1mopar
User

Dec 9, 2014, 8:31 AM

Post #8 of 11 (900 views)
Re: GAS MILEAGE Sign In

when 1st got the truck, I was getting 17.8-18.2 mpg-which is pretty "EFFICIENT" for a truck that old. have had the truck 3 yrs. the mpg went down to around 15-16 when the engine let go-which is understandable. I don't drive much.


I checked the mpg again last week on a run to where my grandkidz live-28.8 miles away. I filled up in AMES-12 miles away on my way to BOONE. I put 49.7 miles on the odometer. the mpg figured to 13.42. I don't know if this is an indication of the ECM "resetting" to the different signals from this engine or what. maybe it's a bit "soon" to be concerned with the difference in mileage.


would you think that the ECM that came with this engine would make that much difference. ECMs operate from the signals they receive from sensors. the sensors that really control mpg are the oxygen sensors & there is no "check/service engine" light on-which a faulty 0/2 sensor would trigger. should I call to see if this engine's ECM is still available-as a possible solution??


thanx


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 9, 2014, 9:46 AM

Post #9 of 11 (896 views)
Re: GAS MILEAGE Sign In

Quote">>should I call to see if this engine's ECM is still available-as a possible solution??<<"


Yes, ask the tech who did the swap if all is compatible or what was done.


You just stated you noticed MPGs dropping before this engine and now checking you math you only put in 3.7 gallons to get your current guesstimate which is not going to be accurate by nature up or down. Please, tell me you've never sqeezed in an extra gallon or two in a full size truck's gas tank despite that you aren't supposed to when the pump shut off by itself?


At those low numbers a QUART off would throw your results off.


Does CEL work? Is it running properly now? You still never said what happened to the engine that was replaced.


Side note is that age and miles really don't effect fuel efficiency without something being wrong or in need. Plain tire pressure absolutely does change rolling resistance and as I mentioned temperatures matter. Air pressure in tires will drop 1 pound for every 10 degrees of the temp in Fahrenheit they are when checked and filled. If checked after driven on a warm day a while ago you could be off 10 PSI now and that would account for a noticeable reduction of gas mileage.


That and a zillion reasons. I live in cold country too. Sometimes a vehicle left outside need to run quite a while to even get ice off windows to see at all to move the thing at all which is always ZERO MPG in the mix/calculation.


So, what I would do is go back to the place that swapped the engine and get any code readings and know if it communicates with this thing now which is pretty good evidence for me that your observations are possibly accurate and just not pleased and already said fuel isn't gasoline anymore it's named gas but full of junk including ethanol that CAN'T get the same MPG as pure petroleum gasoline and you might not know the % you get all the time. It suks IMO. We really don't know exactly what percent of what we are buying.


Again - ask what was done to make this engine work as well as it can from the place that did it and I suggest keep track constantly over many more miles in consideration of shorter trips, longer trips, anything tires, temperatures and a list that never ends. YOU may not have any issue at all is my point,


T



RoboDisko
User

Dec 21, 2014, 3:29 PM

Post #10 of 11 (796 views)
Re: GAS MILEAGE Sign In

If the engine is running properly, then I personally doubt the ECU is causing it to be less efficient. It is possible, but I would suspect other things first.

Without getting seriously into the engine, there isn't much you can do about it's efficiency. Of the top of my head, a few things you can do are:
1. GOOD fuel system additive. In highly neglected engines, this can have a huge impact. In very well maintained engines, it can have little to no impact. You won't know till you try.
2. Good synthetic oil. Can help a few % on mpg at best, but it offers more protection for you engine as well.
3. O2 sensor. This sensor is responsible for telling the ECU if it is sending too much or not enough fuel to the engine, and it wears out over time and abuse. If it hasn't been replaced in many years, or if you don't know, now may be a good time to replace it.
4. Spark plugs. The wrong spark plugs can hurt your fuel efficiency a bit. Most often the manufacture-recommended plug is the best for the engine. Also, if the plugs haven't been changed in a long time, replacing them will most likely help.
5. Engine warmth. Knowing that the engine is more efficient when warm, and adjusting how you drive it to keep it warm when driving as much as possible can have a large impact. For example, doing all your errands at one time so the engine doesn't have time to get cold. This also causes you to drive fewer miles, further burning less gas.

My advice would be to run a quality fuel system additive (Redline SI-1 or Chevron Techron Concentrate plus. Only go with the techron if it is significantly cheaper, which it isn't right now on amazon) and also just give the engine some time. Most ECU's take some time to "learn" the characteristics of the engine they are attached to, and this can take 100's of miles. Also, as has already been said, you mpg samples are so small that any error is huge. Go through a few tanks of fuel, and average you mpg together. I think you will notice a meaningful improvement in mpg after running some quality additive and after measuring over a few tanks. If your mpg is still low, however, then I would probably recommend replacing the spark plugs and O2 sensor(s). If, after doing all of that, you haven't seen a meaningful change in fuel efficiency, then I investigate the ECU.

Also make sure your tires are at, or a few psi over, what is listed on the door. Going a few psi over compromises some traction and handling for a small increase in fuel mileage, which probably isn't a good idea in winter, but you call.

This is just my advice, and I'm not an expert. If one of the experts say something that does not agree with what I have said, they are probably right. I just wanted to add to what they have said.

Also, a bad oxygen sensor can cause poor fuel efficiency without triggering a CEL (check engine light)


(This post was edited by RoboDisko on Dec 21, 2014, 3:38 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 21, 2014, 10:57 PM

Post #11 of 11 (780 views)
Re: GAS MILEAGE Sign In

RoboDisko: Most of your post has been mentioned or asked. Thread is actually getting old now and OP hasn't really responded in a while so probably all over now. Suggestions you made are OK to a point. The MPG testing hasn't had enough miles or multiple times yet to be conclusive of anything.


It's also plain colder now than earlier. Many people don't notice they are using more fuel just warming up longer to average in. Said up there somewhere but hit on it again. THERE ARE OVER 200 FORMULATIONS of fuel to the US alone! They do NOT all have the same possible MPG for assorted reasons. Wish it would state clearly at pumps exactly what you are buying but they don't.


I'm in MA and close to many other states. When checking to the foot how many MPG I can get notice constantly fuel from another state that is more than 50 miles from a city with "X" population is much better, like 10% better! Still could be off on my own calculations some. Those taken over a 400 mile run done many, many times over some years and measures that still insignificant to me personally but shows type of additives in mandatory fuel requirements does mess up actual MPG possible.


Once told weigh a gallon from one place to another. They really do NOT weigh the same per gallon - proof that it's not identical fuel with identical additives that do not all weigh the same. If nothing else it's not fair!


Jeez, if buying anything aren't we allowed to know what it really is? NO!


T







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