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Keving · 10-18-2019, **(Subject: Low fuel economy )**

When I first bought my truck it averaged around 6.5 to 7 mpg. nowadays I'm lucky to get 6 with most of my hand calculated stops being 5.5, I used to drive with the cruise set at 70 but I've been trying to slow it down and see if it helps with no real success. Anyone have ideas on things I can look at? The truck has now been demandated by mr hag however I noticed this drop in fuel economy before this was done.
I've since replaced the air filter and fuel filters which made no change and in the last few months I replaced the imap sensor which also made no change the truck had a detroit dd13 and a 10 speed auto if it helps thanks.

SquareOne · 10-19-2019, **(Subject: Low fuel economy )**

The auto trans is certainly going to hinder fuel mileage -no surprise there-, but if Im reading it right, you're saying the MPG was greater at 70 than when you slowed down? Just because you slowed a little won't translate to better economy unless you're in the correct gear. Top gear @ lower RPM and full load is going to be much worse on fuel and components than less load on the engine through dropping a gear or 2 in order to compensate for the weight you're hauling and terrain you're going through.

Could you post your specs (i.e. rear ratio and tire size). Driving habits are a HUGE contributor to fuel mileage, and although I'm still new to this, it's taken me the last 65k to get to the point I'm at now with still plenty to learn.

- Otherwise you have a unicorn that defies the laws of physics...

Magard · 10-19-2019, **(Subject: Low fuel economy )**

How many miles are on it. Emissions filters are done around 450k so it might be emissions system working harder to keep it clean. I don’t know first hand. I have a buddy that has 5 of them. Seems to be a pattern.

Mattman · 10-19-2019, **(Subject: Low fuel economy )**

Says truck has been demandated.

Is doser injector still hooked up? Could be leaking fuel into exhaust.

Magard · 10-19-2019, **(Subject: Low fuel economy )**

(10-19-2019 )Mattman Wrote: Says truck has been demandated.

Is doser injector still hooked up? Could be leaking fuel into exhaust.

I missed that. Thanks for pointing that out.

Keving · 10-19-2019, **(Subject: Low fuel economy )**

(10-19-2019 )SquareOne Wrote: The auto trans is certainly going to hinder fuel mileage -no surprise there-, but if Im reading it right, you're saying the MPG was greater at 70 than when you slowed down? Just because you slowed a little won't translate to better economy unless you're in the correct gear. Top gear @ lower RPM and full load is going to be much worse on fuel and components than less load on the engine through dropping a gear or 2 in order to compensate for the weight you're hauling and terrain you're going through.

Could you post your specs (i.e. rear ratio and tire size). Driving habits are a HUGE contributor to fuel mileage, and although I'm still new to this, it's taken me the last 65k to get to the point I'm at now with still plenty to learn.

- Otherwise you have a unicorn that defies the laws of physics...

No it started doing this long before I slowed down lol I would be happy to run 70 and get 1 to 1.5 mpg better haha if only it was that simple

Keving · 10-19-2019, **(Subject: Low fuel economy )**

(10-19-2019 )Mattman Wrote: Says truck has been demandated.

Is doser injector still hooked up? Could be leaking fuel into exhaust.

I don't know if that has been blocked off or not however this was a problem before the demandate but either way it would be something to look into thanks!