FredNewell Posted October 21, 2014 Share Posted October 21, 2014 In reading recent posts, I'm seeing that some rigs will do 70 on the interstate, and others will not. Mine will do 70 on flat highway, or 65 on gentle not too steep hills. Others speak (write) of difficulty going over 60 mph, or 55 mph. Mine is no hot rod - and I've been passed by a Winnie Toyota MH that was pulling a motorcycle trailer - up hill.I'm interested in what model year, tranny, and engine combos have for performance. I may trade for a different model eventually.Mine is 1984 4 cyl manual 4 speed. 72 mph on flat interstate all day.Would others mind weighing in?Thanks Quote Link to comment Share on other sites More sharing options...
Bob C Posted October 21, 2014 Share Posted October 21, 2014 I have a 1988 20' Escaper with 22Re and automatic. The loaded weight is about 5700 pounds. I Can go 70 mph on flat ground but don't because my gas mileage really drops. 55 mph without wind on a flat road I get 15+ mpg and at 70 mph it drops to 10. I know this because my daughter was driving while I took a nap. Average driving we get close to 14 mpg with gentle hills and light wind. When planning trips I count on 13 mpg to plan for fuel cost. Quote Link to comment Share on other sites More sharing options...
Totem Posted October 21, 2014 Share Posted October 21, 2014 im usually around 6200 lbs 21 ft sunrader, and my speed varies so much its basically determined by wind, terrain, load and whether or not a truck is in front of me. In brisk wind I can force it to 65 but the thing makes a horrible cricket screeching noise so I prefer 55-60. If the wind is behind my back or downhill I have seen speeds in excess of 70 but its terrifying so again I stay 60 ish if possible. My Mpg usually is 14 - 18 MPG most 16.9 if I average. 22RE automatic 4 banger. Quote Link to comment Share on other sites More sharing options...
zero Posted October 21, 2014 Share Posted October 21, 2014 I've cruised at 70 MPH with my 1988 21' Toyota Minicruiser. 2.4 liter engine and auto trans with no lockup and no OD being used. At the speed the engine is really being pushed, flat highway, no wind against me, and fuel mileage at around 11-12 MPG. Going that fast kind of defeats my purpose of owning a Toyota RV. I try to stick to slower back roads and 55 MPH speeds and get 14-15 MPG. If I had to do a lot of interstate driving at 75-80 MPH - and camp - I'd use my diesel truck with a camper on the back and get 17 MPG doing it. Note that camper has a pop-up roof. Wind resistance is a HUGE issue. Same truck with a fixed high-roof camper @ 75 MPH gets about 14.5 MPG. By the way - I recently met a couple with a brand new Toyota truck and a "lightweight" slide-on camper on back. No water, no heat, no stove. Just a bed, and camping gear. He told me his new truck with a 4 liter V6 gets 12 MPG when he does 75-80 MPH here on a flat Michigan interstate. NOT very impressive figures. That is a truck engine with the latest tech. Quote Link to comment Share on other sites More sharing options...
Totem Posted October 21, 2014 Share Posted October 21, 2014 I think wind resistance has a delta curve that approaches 0 MPG the faster you get no matter how much HP and torque is thrown at the situation. You should be doing better than 14-15 though with a mini at 55 because of this. Time for new distributor cap and plugs, and air filter. Quote Link to comment Share on other sites More sharing options...
zero Posted October 21, 2014 Share Posted October 21, 2014 I think wind resistance has a delta curve that approaches 0 MPG the faster you get no matter how much HP an d torque is thrown at the situation. You should be doing better than 14-15 though with a mini at 55 because of this. Time for new distributor cap and plugs, and air filter. Plugs, filters, cap etc are all fine. So are the valves, compression, etc. All bearings and brakes are fine (no excess drag). I've gotten up to 16.5 MPG with a slight wind at my back and as low as 12.8 MPG with a wind against me. When travelling from Michigan to New York and back, I always get better fuel mileage heading to NY. I assume it's due to the prevailing winds. To be accurate though . . I have probably never made a complete trip 100% at 55 MPH. I've tried but often find the speedo at 60 MPH and then slow back down. This season while driving around the UP, it seemed I always had wind against me no matter which way I went. In fact, I felt like I was going to get blown off the Mac Bridge. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted October 21, 2014 Share Posted October 21, 2014 Aerodynamic drag increases with the square of the speed. In other words, twice the speed, four times the aerodynamic drag. And wind speed should be included. Rolling/mechanical drag is linear. So twice the speed, twice the drag. Quote Link to comment Share on other sites More sharing options...
chefdave Posted October 21, 2014 Share Posted October 21, 2014 My 21ft dolphin with v6 auto averages 18-20 imperial mpg in mixed driving. battling against a 50-60mph head wind watch fuel gauge drop like a stone. have done 95mph down hill in mine must of been on red line for revs. 60mph would be my best cruising speed to allow for inclines and not to drop out of od. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted October 21, 2014 Share Posted October 21, 2014 Were you coming down Ben Nevis to hit 95? Or maybe Hardknott Pass? Quote Link to comment Share on other sites More sharing options...
chefdave Posted October 22, 2014 Share Posted October 22, 2014 Hi derek it was a long straight down hill incline with a following wind. Dolphin was surpising stable. will not be repeating the exercise. staying with 55-60 mph. Quote Link to comment Share on other sites More sharing options...
FredNewell Posted October 22, 2014 Author Share Posted October 22, 2014 Thank you for the data. It appears that most of the rigs are geared to be capable of relative efficiency at approx 60 mph, and can do 70 but with decreased mpg. Quote Link to comment Share on other sites More sharing options...
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