I just got a new T700 with the Paccar MX engine in it about 5,000MI ago. I'm wondering what some of you have been able to do to improve economy on this engine. It started terrible, but got up to about 7.3MPG average while at ~80,000LBS after about 1,000MI. Now it seems to be dropping. The oil level dropped a little (about a quart) so I topped it off with some Lucas I had left over from my last truck and that seems to have helped, but I'm still hard pressed to get 7.1MPG going across OK with no wind and only 75,000LBS gross. (these numbers are based on what I pump; the number shown on the dash is way off).
Kenworth claims I don't have to change oil until 40,000MI...but it already feels gritty, so I'm guessing that is the first thing to do. I'm thinking Amzoil or Royal Purple...any experience with these oils on this engine/alternate ideas?
Also, any other ideas to improve the economy on this engine? I know some of the old C15 engines would get bad fuel economy if someone painted the ground strap...are there any little oddities like that on the MX?
Advice for new MX Owner?
Discussion in 'Trucks [ Eighteen Wheelers ]' started by KillerBug, Jul 27, 2012.
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Good luck! Have not heard any thing good on the mx yet!
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It isn't even broken in yet, it may improve.
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Whatever you do,do NOT put in any oil that you feel like.
Follow KW instructions as to what oil is allowed.
The MX can run very long indeed with it's oil but it has to be right sort off oil.
Do not add oil untill it shows the minimum level on the stick.
For the rest.............it is to early.
You need more miles on the engine before you have to worry about it. -
I've got a 2012 T700 with 107,873 miles on it. It will improve a lot. When they first bought these they were not impressed. This is my second one ( a PAM driver drove over the hood of my first one) and I've seen the mpg's increase over time. I think they are strong reliable engines without trouble. No downtime so far except for sensors and a fuel line that started leaking. Good luck with your new truck. I'm sure you'll find it working out well.
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Use CJ-4 Oil, and do not use additives. Oil is very critical due to the EGR and the DPF. I also wouldn't downshift untill you're at around 1,100 Rpms (depending on your load). Hopefully you're not past 1,500RPMS at your normal driving speed either because these will get thirsty if geared to high for your speed
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It is far too early to make conclusions about fuel economy after only 5,000mls.
I am on my second MX. The first one I drove kept improving until about 50,000mls when it settled down and by then was returning figures of around 1.5mpg better than the Cat C15 it replaced.
I passed it onto another driver after 125,000mls and it has not given any trouble yet.
I started driving another new 386 Pete and MX last month and hopefully it will be the same. -
Just to add that the C15 I mentioned was in a Pete 379 so some of the better fuel economy resulted from the profile of the actual truck and not neccesarily the MX engine.
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As stated above avoid those extra additives. Let that ending break in as KW suggests. I wouldn't expect much improvement till aroun 50k or so.
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I would avoid the Lucas on a new engine. Call Schaeffers in St. Louis, MO. Their oil should meet what Paccar recommends. They will tell you the base oils in each & answer any question you may have. Good people to deal with.
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