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Engine temps are fine, it can go into the 200s on a hill climb and will drop fast when the exhaust brake is running. Can't tell you what RPM to cruise at. Note about what RPM it shifts from 5 to 6 when accelerating slowly, the sweet spot should be just below that. Our 370 ISL likes to run 1400 to 1600 rpms.
-- Edited by bjoyce on Sunday 21st of April 2013 09:00:26 AM
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Bill Joyce, 40' 2004 Dutch Star DP towing an AWD 2020 Ford Escape Hybrid Journal at http://www.sacnoth.com Full-timing since July 2003
Standard rule of thumb is... The slower you go the better your fuel mileage. Some will argue that they have a sweet spot well above sanity but physics says that's not likely. I heard tell that the Spaniards use to go thousands of miles on a galleon. My motor is quite a bit bigger than the ISB but I find that running 55 is a great speed for comfort and efficiency. Slower than that causes too much stress for other motorists. I don't like running my motor faster than about 1700 rpm and if I can cruise between 1400 and 1600 I am happiest. The power curves on the ISB look similar to the larger motors.
-- Edited by MarkS on Saturday 20th of April 2013 12:00:37 PM
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MarkS & Jackie MSgt, USAF, Ret 2004 Volvo 780 530 HP Cummins 13 speed 2014 Trilogy 3650RE fulltime since Oct 8, 2016
We have the ISL engine and I like to run about 1500 rpm. That puts me at almost 60 mph, but more important, the transmission drops into 6th gear at around 58 mph. I would shoot for just above whatever speed is required to drop your transmission into high gear.
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2018 Thor Windsport 35M -- 2018 Camry Toad
-- USAF Retired -- Full-timing since December 2007 - Part-Timing since July 2011
The engine has an operating range that makes it efficient. If you lug the engine in a higher gear, it may be less effecient than running a higher RPM in a lower gear or higher speed.
I have a slightly larger (ISB340) engine, but the 1400-1600 RPM sounds about right. I find that I get the maximum MPG at between 58 and 62 MPH. Any less and I shift to 5th... any more and I get uncomfortable and lose MPG. On reasonably level terrain, I can be between 8.0 and 8.5 MPG.
Sounds like we're all on the same page, 60 MPH at 1500 RPM. Temps run around the 175 to 180 on flat and level and will rise on the up hills. Downshifting on the hills and keeping the RPM up will help a little with temps.