Yea a lot of forums said keep the rpm under 2000, was like the universal suggestion lol. 70mph is right around 2000 rpm and 55mpg is right at 1500rpm. 60mph should be around 1700rpm which seems to be a pretty solid sweat spot for this engine.
According to this site, the peak torque is around 2000 rpm and looks like 1700-2200rpm is a pretty solid area to try to stay in for torque output. Almost makes me think going 55mph might actually hinder mpg slightly vs 60mph, atleast with a mild load. I guess I hit roughly the ideal rpm range with out really knowing. My first thought was 55mph on the expressway, but figured the 5mph faster would be worth it for the long trip.
7.3L Power Stroke Diesel Specs & Info
Also really interesting the IDI peak torque is at 1400 rpm. People always say how bad the MPG is with the IDI engines, but I bet they are running them way too high of rpm. Based on the chart, I'd guess 1400-1800rpm would be ideal for the IDI engines. I guess that still falls under the under 2k rpm suggestion xD.
A hotter thermostat might be a good idea, my engine oil seemed to hold a pretty cool temp, not sure how hot is too hot though. Online is saying targeting 250f or lower is best and around 275 is when the oil starts to break down. I saw around 214 peak on my trip with a small load so could probably bump the water temp up a bit (thermostat). I know the diesel likes it more, but trying to keep in mind the other fluids, wiring, connectors etc. It's crazy how trashed harnesses are from vehicles in hotter areas of the country, here they might get a little stiff but in the major sun in like AZ or FL the harnesses can get so hard any flexing breaks the insulation. I assume that's from higher average temps and hotter under hood temps.
The owner's manual has a lot of good suggestions, but it's always very conservative on most things because of possible lawsuits and such. I might not be a diesel expert, but I've worked on vehicles and engines since I was about 10, same story with my dad (he did it professionally). I just turned more to electronics and computers for schooling, got my dream job, got bored after 4 years (midnights at a large corp) and moved on. Anyway, I've always learned to ask why instead of blindly following ideas/things. So I'm really wondering, why is it suggested to idle a diesel to cool it down vs just turning the engine off and letting it air cool? I'm sure there's a LOT of people that don't follow that suggestion and never heard of really any engine issues with these engines. Generally in parking lots and my road/driveway I'm idling for 2 or so mins even though I'm moving still so I'm naturally getting some of the cooling effect with out trying. Is there a target temp to try to hit, I don't really have a coolant reading (yet), but I can watch engine oil temps. Next time I drive it far enough to hit max oil temps, I'll have to let it idle and see what it drops to.
I'd assume the suggestions for the other diesel trucks would be similar, the ford one says to not pull start or roll start in gear as it damages the cat. My truck doesn't have one since it's the older model, but I'm sure the newer diesels have it. If that's the case, then engine off coasting and restarting with the momentum of the truck is a no go to the manual. If the engine rpm goes high enough, it should be the same thing as using the starter.
It seems like some of the best mpg tactics are a compromise, like going around corners faster but still safely adds wear to bearing and tires, but the fuel saved in theory would be greater.
With the power stroke, not really planning used oil or trans fluid, atleast haven't thought about it too much. The IDI engine would be pretty ideal for that kind of setup since I'm sure the injector nozzles are larger since it runs a lower injection pressure and also is ran through a mechanical injector pump. I'm not against a mix in summer though, like I was planning to research what grade of filters and build atleast some sort of simple setup (bucket + gravity feed through the filter or whatever) to filter the used engine oil from the truck to dump in the tank. I was thinking like 5-10%. On the old VW diesel engines (like 80's era) it's known that will run on vegi oil and similar by just preheating the fuel. I've seen a few videos on it, they generally run the car on diesel to warm it up, then switch to the vegi oil and before turning it off they switch back to diesel to purge the system for the next cold start. I know where 55gal is that I could probably get free, but it's from a restaurant that served beef products and other meats so the oil has animal fats in it. The guy was trying to make his own biodiesel but ran into issues because he didn't account for that. I think he ran on the stuff going home (he's from way up north of me). Used engine oil and trans fluid seems more logical since there's a ton of the stuff, but I also live in an area that gets cold winters and people burn the stuff for heat sometimes. It seems to value around $0.50-$1 per gal, but free might be possible from a business.
Anyway, I should mess around with some areo mods before long. I can't do the belly pan until all the fluids are set. I probably need some axle seals and such too and I think one hub had some grease on it so it's seal is probably junk too. Plan is fix the leaks, change the fluids to some really good synthetic stuff and figure out a belly pan/skid plate setup. Clearly can't do much about the axles, but figured the rest I could do something about. I plan to undercoat the truck then add the belly pan with the idea that the salt/water should hit the belly pan mainly and likely not wash off the undercoating. Probably still be a yearly inspection on the undercoating and such, so I need to make the panels removable. I'm thinking of making it of metal since this truck isn't exactly light and bottoming out would destroy just about anything else. Current idea is some flat bar (maybe small square tubing) for the basic frame/shape and thin gauged sheet metal to skin it. Primer, paint, then undercoat the belly pan too. Might be a bit of a mess to take off, but it shouldn't rust out. I used coroplast on my corolla for a 1/2 engine bay belly pan and it did work out pretty well, but the distances where real short and I had a center support to rivet it to. I'm thinking front will be a standard skid plate with thicker metal, center could probably be plastic or light metal and same with the rear. I've thought about the front end as well, I could run an air dam below the bumper as long as it's flexible and would hold up to steep drive ways (common in my area). First thing that comes to mind is conveyor belt, but it's heavy. Landscaping plastic trim would probably work for ~4in of drop.
I went pretty crazy on my corolla, sealed the hood, covered up most of the front end, sealed around headlights, etc and most of it I saw effectively no gain. Passenger mirror delete was a bigger gain than sealing up the front end. With this truck being a brick, I wonder if it would help much sealing around headlights and such, or focus on other areas (mainly the bottom). Next biggest loss is probably the topper, but it seems to be working out pretty well as is for now. I'm sure with out the topper I'd be getting worse mpg based on what I read online for other people's mpg at slower speeds on the express way. Best I saw was something like 19mpg going 65-70mph with 3.55 gearing.
Anyway, I'll have to poke around the forums for some people with experience running used engine oil/trans fluid in these engines. I don't drive a lot, but when I go on longer trips it would be nice to burn cheaper fuel =).