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I am driving my Brother's 2002 4.0L gas ford ranger truck 5 speed manual transmission. What RPM should I shift at for best fuel economy. Also what RPM should I not let the truck go below while driving to prevent possible damage. Assuming that I am not carrying or pulling anything with the truck, everything is stock, and flat ground. I am concerned about the oil pump not having enough psi to lube parts correctly when being used, or other things that cause damage that I am unaware of.

ps. I am really looking for what should be done and not what people do. So please do not respond to me on what RPM you shift at as reason. Looking for explanations, I would also like rule of thumb based on motor size and fuel type.

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  • This question is kinda hard to answer subjectively because it has a lot of variables. I'm not voting to close it off but you might not get a very definitive answer. I can't seem to find a way to answer it properly, but surely someone smarter like @Paulster2 will do.
    – race fever
    Commented Mar 22, 2016 at 23:58

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As @racefever states, this is really subjective and hard to answer. I will try to do my best though.

Most of this is going to be done by feel. Every vehicle, even those of the same make/model, will have a different RPM at which it will get the best gas mileage. What I can tell you about when to shift, though, is keep it in the highest gear without lugging the engine. This will keep the engine at its lowest RPM for whatever speed you are at. Drive the engine up to a given RPM and shift. Depending on the vehicle, this could be anywhere from 2500-4500rpm ... it's just something you are going to have to get used to. After a short period of time, you'll get muscle memory as to where to shift and you won't even notice you are doing it ... it will just come natural. Unless you are taking the engine to the redline, you aren't going to cause the engine any damage.

As far as oil pressure goes, remember that an engine will run just fine at idle. You will not drive at idle, therefore you should never have to worry about oil pressure as long as the engine is mechanically sound and there is enough oil in the sump. If anything happens where the low oil pressure light comes on, then you need to worry about it. Even engines with an oil pressure gauge will have an idiot light which comes on if the oil pressure is too low. As long as your brother has kept good maintenance on the truck, this really is nothing to even start worrying about.

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    Since @OP is focusing on getting the best fuel economy he should also pay attention to his driving habits. Keeping your distance, cruising on neutral and using the brakes the least amount possible helps. Since this is a Ranger you could maybe get a difference of 3-5 MPG by modifying your driving habits. Since this is the 4.0, the torque peak is at @ 3000 RPM for that particular year (with 238 pounds of torque). Shifting around 3000 RPM will work for low load conditions (not going up a hill or passing on the freeway). Engine specs: therangerstation.com/tech_library/4_0_Page.shtml
    – race fever
    Commented Mar 23, 2016 at 0:30
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    @racefever - Very valid points! Thank you for your comment :o)
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Mar 23, 2016 at 2:03
  • You are welcome. I'd be nicer to you if you weren't a chevy guy (ford guy here). ;-)
    – race fever
    Commented Mar 23, 2016 at 15:26
  • Thanks for therangerstation page race fever. :) I liked the common problems section since that may save a ton of money in the future. :)
    – Lex Sarrasin
    Commented Mar 23, 2016 at 15:38
  • I was reading on another form where two mechanics seem to be having it out on a similar question to my own without saying the type of vehicle. One mechanic said that as long as the RPM is above idle RPM the oil pump should be running at a level that does not damage the engine. The other mechanic said that when the vehicle is moving it has a load on the system and the system demands more oil pressure to prevent parts from being damaged. Said something about starting the car from a stand still in 3rd with no gas and you will hear some parts hitting each other.
    – Lex Sarrasin
    Commented Mar 23, 2016 at 15:57

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