I have a new car (RAV 4, automatic). I live 6 miles up a steep canyon. Coming down the canyon I never have to put my foot on the gas. Would it be dangerous to turn the engine off (I still have control over the power steering and brakes) and coast to save gas?
The amount of gas you would save would be negligible, and you would lose the braking power of the engine, which would result in more wear on the brakes.
Extremely dangerous. Your power brakes have one - two pumps and then become manual brakes and really bad ones at that. Also all the safety systems are shut off with engine shutdown that can save you.
Well, now, I think the main issue is that they don't understand how a modern automatic transmission works, which is hardly something we can hold against someone.
The OP is probably thinking that if you leave it in gear, the momentum of the car will keep turning the transmission and engine, which would keep turning the power steering pump and generate vacuum for the power brakes. This would be the case in a manual transmission car or some of the old automatics with the extra pump, although this practice on a carbureted car could lead to one's muffler exploding. But on a modern automatic, the pump that generates the pressure is run on the engine and so it doesn't work the other direction, which is also why you can't push-start an automatic and why it's a bad idea to tow with the drive wheels on the ground.
No, you DON'T still have control over the power steering (unless it's electric) and brakes. Danger, Will Robinson! Besides, the extra wear and tear on the starter would probably be more than any potential fuel savings. At idle, the engine uses very little fuel.
If you coast in gear with the engine running, the computer will deliver minimum fuel to the injectors.
Try to calculate the amount of gas you save by shutting down. It is likely to be pennies per month, maybe less. Leaving aside any risk or damage to the transmission by coasting with the engine off, you should still see that there is insignificant fuel savings. Not worth it.
Did you ever read about people who started out on a trip and were not seen again until a hunter or hiker just happened to spot the car a year later? Some of them may have tried something like you want to try. If you absolutely have to try it, I don't have any idea what to say to keep you and other drivers safe. I'm still alive but that was just being lucky. I stopped before crossing a puddle at midnight in the rain. I rolled the window down and put my head out to see better and it turned out to be a 200 foot wide gravel pit. To get this into your reality, if a cow walks out in front of you; will all your cars systems be ready to keep you from crashing? I don't know. Antilock brakes? Any brakes? Good luck.
Off topic, however, with a hybrid car there are many times when the engine is turned off. I don't know which (if any) of the hybrid variants do this, but a hybrid could be coasting down a hill with the engine turned off. Steering and brakes are electric, and regenerative braking keeps your speed under control while recharging the battery.
True, but the hybrid vehicles were designed for the engine to automatically turn off only at certain times (mainly when stopped in traffic.) I can guarantee going down a canyon is not one of those times, and certainly not with a RAV4.
This is one of the best examples I have ever seen of being "penny wise and dollar foolish". The pennies that would be saved in gas consumption will be more than overwhelmed by the extra wear and tear on the starter and the lack of lubrication to part of the transmission.
And, then, when you factor in the safety issue of having NO POWER ASSIST for the brakes and the steering, it becomes just plain foolish to even consider this.
Called Oklahoma Overdrive back in the day. And back in the day, a lot of "Okies" ended up over the side. Of course in those days it was manual tranny. And the engines were not turned off, the car was just put into neutral.
Dangerous, yes. Stupid, yes. Having said that, I leave the car running but still put my MANUAL tranny into neutral on downhill runs that I am VERY familiar with. Saves me, maybe $2 in a year, but makes my old Okie roots feel better.
Does Oklahoma actually have hills long and steep enough to be dangerous to coast down?
I do it all the time but our hills in Texas, (Baja Oklahoma) are mostly just steep enough to maintain the speed limit and I have a manual transmission. Since the owner's manual ok's dinghy towing behind a RV with the transmission in neutral, I figure it's ok when gravity is doing the towing.
Don't really know about "Real Oklahoma," since I haven't been there since I was 4. I am mostly going off "family history" and what I have read from John Steinbeck. But here in Oregon, we have plenty of Hills, which in other parts would probably be called mountains.
Does Oklahoma actually have hills long and steep enough to be dangerous to coast down?
My wifes aunt uses that method. And one day while visiting my wifes Mom she did it and got in a accident. She didn't understand why it didn't work the way it does at home in Central Florida. Well considering that Space Mountain at Disney World is the Second highest mountain in Florida....it can't be too dangerous...
Unless I misinterpret your post, you are descending a hill in an RV towing a ('dinghy' or toad') with the transmission in neutral? I hope you mean ONLY the dinghy is in neutral.
02/13/2008 9:07:44 AM
