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Fuel economy
Posted: Sat Apr 18, 2009 8:59 pm
by Hombrey
Guys interested in getting to the bottom of this. Just filled my tank and after setting the trip it took 44 litres to do 254ks. Its a TD42 non turbo, does not pour out black smoke, has vurtually no blow by, no leaks (anymore) done 276,000ks. That seems a lot of gas to me...wheres it goin?? I'm actually looking for the stuff pouring out somewhere

. Any ideas/help would be great. Does seem a little low power wise to, but I'm new to diesels and 4.2s so not really a good judge on this stuff.
Re: Fuel economy
Posted: Sat Apr 18, 2009 9:08 pm
by tallsam66
Could be several things.lots can influence economy.
Most common is
Air Filter.
Fuel Filter.
Re: Fuel economy
Posted: Sat Apr 18, 2009 9:35 pm
by Hombrey
Yeah also running 33's so not sure if the odometer is calibrated. Would 33's be causing a lower than expected reading?
Re: Fuel economy
Posted: Sat Apr 18, 2009 10:37 pm
by KiwiBacon
Hombrey wrote:Yeah also running 33's so not sure if the odometer is calibrated. Would 33's be causing a lower than expected reading?
An uncalibrated odometer is a major problem. Check it against a known distance, some state highways have measured odometer checks on them.
Go up 10% in tyre size without correcting the odometer and you'll record 10% worse fuel economy even if your actual consumption doesn't change.
Re: Fuel economy
Posted: Sat Apr 18, 2009 11:40 pm
by flyingbrick
tallsam66 wrote:Could be several things.lots can influence economy.
Most common is
Air Filter.
Fuel Filter.
Agreed.
I gave my truck a birthday- paid a place to do an engine flush + change engine oil/fuel filter/air filter and the difference in power was incredible.
diesels love clean air filters.
Re: Fuel economy
Posted: Sat Apr 18, 2009 11:41 pm
by tallsam66
Easiest way to check speedo is to borrow a GPS off someone.
Re: Fuel economy
Posted: Sun Apr 19, 2009 2:30 am
by Taz
flyingbrick wrote:diesels love clean air filters.
Get a Uni filter and that way you can clean it as often as you like to keep up performance.
Don't know if it makes a difference to anything but I do my diesel filter whenever I do my oil filters to, rather than every second time.
Edit: Also double check the oil filters when you get them done somewhere else. Last time I got mine done at oil changers in hornby a knock started on start up for about five seconds, so I changed them again to some ripco ones and it went away. They didn't want to know about it when I bought it up with them but its their loss of business.
Re: Fuel economy
Posted: Sun Apr 19, 2009 8:58 am
by tallsam66
I generally buy either Repco or Ryco filters (RZ9 or Z9).
Recently i brought some others on trademe (Samura C-1112)..but the filters are about an inch shorter.
Since fitting it ive noticed an approx 10% decrease in economy just as i do when im about 1000km away from an oil change.
Re: Fuel economy
Posted: Sun Apr 19, 2009 10:41 am
by KiwiBacon
Taz wrote:flyingbrick wrote:diesels love clean air filters.
Get a Uni filter and that way you can clean it as often as you like to keep up performance.
Don't know if it makes a difference to anything but I do my diesel filter whenever I do my oil filters to, rather than every second time.
Edit: Also double check the oil filters when you get them done somewhere else. Last time I got mine done at oil changers in hornby a knock started on start up for about five seconds, so I changed them again to some ripco ones and it went away. They didn't want to know about it when I bought it up with them but its their loss of business.
Cut out the guesswork and put a restriction guage on your filter. It tells you how much pressure drop is across the filter. I use a donaldson informer.
Filters clean better as they get more filled, but if they get too clogged then your engine can suck dust through them.
Re: Fuel economy
Posted: Sun Apr 19, 2009 1:41 pm
by darinz
KiwiBacon wrote:Hombrey wrote:Yeah also running 33's so not sure if the odometer is calibrated. Would 33's be causing a lower than expected reading?
An uncalibrated odometer is a major problem. Check it against a known distance, some state highways have measured odometer checks on them.
Go up 10% in tyre size without correcting the odometer and you'll record 10% worse fuel economy even if your actual consumption doesn't change.
A GQ with 33's is reading within about 1%. I run 33's on my wife's GQ with standard 4.1 diffs and on the GPS it was as close as it was possible to judge. (gps is in my other truck) It was reading about 101km on the gps when doing 100 on the speedo. So just think of all the RUC that you guys with 31's are paying that you don't need to!!
Re: Fuel economy
Posted: Sun Apr 19, 2009 2:10 pm
by KiwiBacon
darinz wrote:A GQ with 33's is reading within about 1%. I run 33's on my wife's GQ with standard 4.1 diffs and on the GPS it was as close as it was possible to judge. (gps is in my other truck) It was reading about 101km on the gps when doing 100 on the speedo. So just think of all the RUC that you guys with 31's are paying that you don't need to!!
Did you check the odometer accuracy as well as the speedo?
They are calibrated differently, most speedos have a 5% error at 100k/h (reads 100, you're doing 95) with the odometer accurate.
Re: Fuel economy
Posted: Mon Apr 20, 2009 12:34 pm
by darinz
Nah, I wasn't really worried about that. On my winch truck it has had the speedo calibrated for 35's but I haven't checked the odometer. There is only one sensor so the relations hip between then will still be relative.