Worried about freeway fuel consumption recently. Getting 16 MPG...

yogi799 · 12-30-2012, 10:55 PM

So recently I took another annual trip from NY to FL and to my horrible disappointment my mileage hardly exceeded what I get in the city! I typically stayed with the traffic at about 75-80 MPH and on average got only 15-16 MPG!

Let me know what you think. Here are the circumstances and the speeds with corresponding MPG. Should I be concerned? I think I used to get avg of 21 MPG on those trips and I've taken 3 of them before with the only difference being slightly younger (lighter) kids.

The X was packed with roughly 3.5 adults (2 adults and 4 small kids below 10), some cargo (not massive amounts!) and AC was not used on the majority of the trip. The tire pressure is rather high at around 40 PSI. Air filter is new. Spark plugs have never been changed. The X has tons of power indicating good health of the engine? No problem starting or reaching any speed. Sounds very well as well. No wheels are too hot (I used to have sticking brake pads problems which made the wheels hot but I've solved them, I think, wheels are just warm to the touch)

70 MPH - 18 MPG
75 MPH - 16 MPG
80 MPH - 14 MPG

On one day I got 22MPG at 55 MPH.

Those measurements are according to the trip computer not manual check, BUT the next paragraph explains that the poor range confirms the accuracy of the trip computer.

So I am a bit concerned as I could not even get 300 miles on a tank and I felt like I am dumping gas out of a tailpipe - I think I remember getting 350 miles on freeway trips before!

Is it possible that each 5 mph is killing my MPG so much or is something wrong? I also own a new V6 sedan and such increments make almost no difference in the MPG.

It is a 2003 MDX with 140k miles on it.

Tyler · 12-30-2012, 11:20 PM

Spark plugs need to be changed, out of curiosity, at what mileage did you take your trips at previously? are you putting premium in it? Between my 02 and 03 x's, I get about 19.5 mpg when cruising at 75-80.

yogi799 · 12-30-2012, 11:27 PM

114 k and 127 k

No, regular gas. I believe I used regular in the last 3 trips as well though...

INGunGuy · 12-30-2012, 11:40 PM

Quote:

Originally Posted by yogi799

114 k and 127 k

No, regular gas. I believe I used regular in the last 3 trips as well though...

I have a 2001 and I noticed a major loss of MPG when I tried to use regular unleaded. Oh and for the record, I am spending 3/4 of a cent LESS per mile using premium versus regular unleaded.

INGunGuy

yogi799 · 12-30-2012, 11:45 PM

I hear you guys but the fact is that I used to get about 20 MPG on regular and now down to 15-16. Would spark plugs make any difference (the engine seems to perform well, except the MPG)?

Tyler · 12-31-2012, 12:04 AM

Yes, spark plugs would make a difference. I believe Acura suggests to change the iridium spark plugs at 100k. I prefer to change mine every 60k, but that is my personal preference. Plus carbon build up can happen around the sparkplug which can make it a real bear to take out. A buddy of mine did not change his on his Nissan Altima (2008) and wanted me to change them at 165k and they were baked right it Lol.

INGunGuy · 12-31-2012, 12:05 AM

Quote:

Originally Posted by yogi799

I hear you guys but the fact is that I used to get about 20 MPG on regular and now down to 15-16. Would spark plugs make any difference (the engine seems to perform well, except the MPG)?

Yes, the spark plugs are not firing as "hot" as they should so your fuel economy suffers. Also as for using premium unleaded, the fuel economy gained outweigh the cost difference.

INGunGuy

yogi799 · 12-31-2012, 12:09 AM

What puzzles me is why the heck am I able to get 21-22MPG at 55mph and the mileage tanks at higher speeds if the spark plugs (or anything else for that matter) is not right?

And yes, I wanted to start using Premium again but in Ontario the price difference is huge and I did not know if it's worth it...

INGunGuy · 12-31-2012, 12:22 AM

Quote:

Originally Posted by yogi799

What puzzles me is why the heck am I able to get 21-22MPG at 55mph and the mileage tanks at higher speeds if the spark plugs (or anything else for that matter) is not right?

And yes, I wanted to start using Premium again but in Ontario the price difference is huge and I did not know if it's worth it...

If the spark plugs are worn out it really starts to show at higher speeds where the engine is working harder. I say it is high time for a spark plug change. I have a 1997 Ford Escort that I was getting 32 - 35 MPG at 80 MPH I dropped to around 28 MPG I pulled the plugs and they were shot. I changed the plugs, and immediately my MPG went to 32 - 35 MPG at around 80 - 85 MPH. If I were to keep my speeds to 65 MPH, I was getting around 35 - 36 MPG so the gain for the speed reduction wasnt worth the extra time on the road. I travel 60 miles one-way to work every day so I try and keep my speed a bit higher since I do it every day...

INGunGuy

INGunGuy · 12-31-2012, 12:24 AM

Quote:

Originally Posted by yogi799

What puzzles me is why the heck am I able to get 21-22MPG at 55mph and the mileage tanks at higher speeds if the spark plugs (or anything else for that matter) is not right?

And yes, I wanted to start using Premium again but in Ontario the price difference is huge and I did not know if it's worth it...

Another thing that I have noticed is that if I set the cruise in my 2001 MDX I get around 24 - 25 MPG at 75 MPH which kind of surprised me. But if I try and keep the speed at 75 without using the cruise I am getting 21-23 MPG... which is another surprise.

INGunGuy

yogi799 · 12-31-2012, 12:29 AM

OK, thanks. I am reading other old threads and see a variety of reports. Some ppl get 20+ at 75mph, some get 16 like me now. Weird. I always use the cruise.

I already got new spark plugs and will change them asap. Not to hijack my own thread, but am I looking at a nightmare of a job since it's got 140k on the clock? Should I do anything special when replacing them OR can they break if I apply to much force to loosen them up? Last thing I want is to damage my engine because of this simple omission.

INGunGuy · 12-31-2012, 12:34 AM

Quote:

Originally Posted by yogi799

OK, thanks. I am reading other old threads and see a variety of reports. Some ppl get 20+ at 75mph, some get 16 like me now. Weird. I always use the cruise.

I already got new spark plugs and will change them asap. Not to hijack my own thread, but am I looking at a nightmare of a job since it's got 140k on the clock? Should I do anything special when replacing them OR can they break if I apply to much force to loosen them up? Last thing I want is to damage my engine because of this simple omission.

They should not be too difficult to remove... Just dont force the issue...

INGunGuy

Tyler · 12-31-2012, 01:01 AM

They should be okay, if there is a lot of buildup I prefer to use Marvel's mystery oil and let it soak for a bit, then come few hours later. It works to loosen up the buildup, but I think you should be okay with out it. Remember always start the spark plug by hand (using extension) that way you will not strip the threads. Righty tighty lefty loosey...

yogi799 · 12-31-2012, 01:05 AM

Maybe a dumb question, but I am about to leave FL back for up north tomorrow... Would it hurt in any way if I just got the three front ones replaced? I may simply run outta time to do all six. Or better not do any OR all at once?

INGunGuy · 12-31-2012, 01:50 AM

Quote:

Originally Posted by yogi799

Maybe a dumb question, but I am about to leave FL back for up north tomorrow... Would it hurt in any way if I just got the three front ones replaced? I may simply run outta time to do all six. Or better not do any OR all at once?

I would take the time to get all 6 replaced. I myself in all the years of shade-tree mechanics that I have accomplished have never not replaced every spark plug. Also to make the next removal a little easier, put some anti-seize compound on each plug.

INGunGuy

12-30-2012, 10:55 PM	#1 (permalink)
yogi799 Registered User Join Date: Oct 2003 Location: Ontario, Canada Posts: 402	Worried about freeway fuel consumption recently. Getting 16 MPG... So recently I took another annual trip from NY to FL and to my horrible disappointment my mileage hardly exceeded what I get in the city! I typically stayed with the traffic at about 75-80 MPH and on average got only 15-16 MPG! Let me know what you think. Here are the circumstances and the speeds with corresponding MPG. Should I be concerned? I think I used to get avg of 21 MPG on those trips and I've taken 3 of them before with the only difference being slightly younger (lighter) kids. The X was packed with roughly 3.5 adults (2 adults and 4 small kids below 10), some cargo (not massive amounts!) and AC was not used on the majority of the trip. The tire pressure is rather high at around 40 PSI. Air filter is new. Spark plugs have never been changed. The X has tons of power indicating good health of the engine? No problem starting or reaching any speed. Sounds very well as well. No wheels are too hot (I used to have sticking brake pads problems which made the wheels hot but I've solved them, I think, wheels are just warm to the touch) 70 MPH - 18 MPG 75 MPH - 16 MPG 80 MPH - 14 MPG On one day I got 22MPG at 55 MPH. Those measurements are according to the trip computer not manual check, BUT the next paragraph explains that the poor range confirms the accuracy of the trip computer. So I am a bit concerned as I could not even get 300 miles on a tank and I felt like I am dumping gas out of a tailpipe - I think I remember getting 350 miles on freeway trips before! Is it possible that each 5 mph is killing my MPG so much or is something wrong? I also own a new V6 sedan and such increments make almost no difference in the MPG. It is a 2003 MDX with 140k miles on it. __________________ LogMyMpg's Sponsor

12-30-2012, 11:20 PM	#2 (permalink)
Tyler Registered User Join Date: Apr 2012 Location: Manchester, New Hampshire Posts: 204	Spark plugs need to be changed, out of curiosity, at what mileage did you take your trips at previously? are you putting premium in it? Between my 02 and 03 x's, I get about 19.5 mpg when cruising at 75-80. __________________ 02 Black MDX 03 Blue MDX 88' Volvo 240 - 445,000 mi. 07 Civic Si

12-31-2012, 12:04 AM	#6 (permalink)
Tyler Registered User Join Date: Apr 2012 Location: Manchester, New Hampshire Posts: 204	Yes, spark plugs would make a difference. I believe Acura suggests to change the iridium spark plugs at 100k. I prefer to change mine every 60k, but that is my personal preference. Plus carbon build up can happen around the sparkplug which can make it a real bear to take out. A buddy of mine did not change his on his Nissan Altima (2008) and wanted me to change them at 165k and they were baked right it Lol. __________________ 02 Black MDX 03 Blue MDX 88' Volvo 240 - 445,000 mi. 07 Civic Si

12-31-2012, 01:01 AM	#13 (permalink)
Tyler Registered User Join Date: Apr 2012 Location: Manchester, New Hampshire Posts: 204	They should be okay, if there is a lot of buildup I prefer to use Marvel's mystery oil and let it soak for a bit, then come few hours later. It works to loosen up the buildup, but I think you should be okay with out it. Remember always start the spark plug by hand (using extension) that way you will not strip the threads. Righty tighty lefty loosey... __________________ 02 Black MDX 03 Blue MDX 88' Volvo 240 - 445,000 mi. 07 Civic Si

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12-30-2012, 11:27 PM	#3 (permalink)
yogi799 Registered User Join Date: Oct 2003 Location: Ontario, Canada Posts: 402	114 k and 127 k No, regular gas. I believe I used regular in the last 3 trips as well though...

12-30-2012, 11:45 PM	#5 (permalink)
yogi799 Registered User Join Date: Oct 2003 Location: Ontario, Canada Posts: 402	I hear you guys but the fact is that I used to get about 20 MPG on regular and now down to 15-16. Would spark plugs make any difference (the engine seems to perform well, except the MPG)?

12-31-2012, 12:09 AM	#8 (permalink)
yogi799 Registered User Join Date: Oct 2003 Location: Ontario, Canada Posts: 402	What puzzles me is why the heck am I able to get 21-22MPG at 55mph and the mileage tanks at higher speeds if the spark plugs (or anything else for that matter) is not right? And yes, I wanted to start using Premium again but in Ontario the price difference is huge and I did not know if it's worth it...

12-31-2012, 12:29 AM	#11 (permalink)
yogi799 Registered User Join Date: Oct 2003 Location: Ontario, Canada Posts: 402	OK, thanks. I am reading other old threads and see a variety of reports. Some ppl get 20+ at 75mph, some get 16 like me now. Weird. I always use the cruise. I already got new spark plugs and will change them asap. Not to hijack my own thread, but am I looking at a nightmare of a job since it's got 140k on the clock? Should I do anything special when replacing them OR can they break if I apply to much force to loosen them up? Last thing I want is to damage my engine because of this simple omission.

12-31-2012, 01:05 AM	#14 (permalink)
yogi799 Registered User Join Date: Oct 2003 Location: Ontario, Canada Posts: 402	Maybe a dumb question, but I am about to leave FL back for up north tomorrow... Would it hurt in any way if I just got the three front ones replaced? I may simply run outta time to do all six. Or better not do any OR all at once?

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