Red light Nuetral Help or hurt?
 

I've started putting whatever car I'm driving in nuetral at red lights The theory behind it is when your car is in drive it wants to pull a little so it strains your engine by trying to pull therefore using gas However when it's Not in Drive it wont pull at all?

What do you guys think any legitamite increase behind this? even if it's 1/10 of an MPG it'd still be worth it right?

According to my Scanguage II, my 3.0l Mitsubishi uses about .45 gph idling in drive once warm. In Neutral it uses 0.35 gph.

My initial thought on the subject is that by slowing down the engine it would use less fuel. Which is probably applicable to carburators, not sure.

New cars with Idle Air Control valves try to keep a constant idle rpm. So when you load the engine down in gear, it opens a small secondary throttle & gives it more go juice.

This is only my thoughts, if they are wrong, someone please correct me.

Don

Assuming you're talking about an automatic, most automatics idle slightly lower in neutral than they do in drive. So yes, you'll be using less gas than you would by holding the brake down. Probably nothing too noticeable, but it's better than nothing.

I always put it in neutral in automatics because my first car developed a pretty big rattle when it was stopped in drive, but it went away when I put it in neutral, so it's just a habit now.

Carb will still use more fuel because the engine is partially loaded, so it needs more power at either the same speed or even a lower speed to maintain it's condition (running). More power out = more fuel in.

IACV's are the only idle source on FI cars, the throttle plate is fully closed when you're not using the pedal, so the IACV just opens further to compensate for load.

Regarding OP's question - It does use less fuel, but not as much less as just shutting your car off. If you can time the light and shut the engine off and coast up to the light from 500 feet away (provided you're going to sit at it anyway), you'll save several seconds worth of fuel until the opposing light turns yellow, then you restart and you're ready to go by the time your light is green again.

Either method is relatively little gain, but they both work to some extent. I almost always coast to lights. Hell, I turn the engine off when I'm coasting to bleed off speed.

So christ what ur saying is it's an alright idea?

If you prefer a simplistic answer, yes.

You're not in danger of hurting anything by doing it, and it can save you fuel, although minimal.

It can't hurt, it can only help.

I've been doing it for decades but not primarily to save gas. The worst enemy of an automatic transmission is heat. If you can take a load off the transmission, especially in summer, so much the better. Considering that rebuilding a tranny is one of the most expensive repairs, I like to avoid problems. I also drain and refill it every six months. Transmission fluid is relatively cheap - again it can't hurt, it can only help.

Some think that this might actually hurt more than help... I'm on the fence about that, but I do think it's a waste of money. In six months, unless you drive cross-country twice a month, you haven't even broken in good fluid.

That's where the thought that it does more harm than good comes from. If the fluid isn't broken in (additive package isn't fully released), it's not working as well as it could.

Considering that the only time I ever change fluid or filter is if I have to pull the engine, axle, etc... something that will cause fluid to leak out, which is seldom and far between, I don't think it's really necessary to change the fluid even as often as the MFG says it is (60k, is it?). I've never had an auto fail, and I beat the hell out of them.

The new Hyundai/Kia 6 speed AT shifts automatically into neutral when stopped. The AT in the Mitsu Outlander does it too. If the OEMs do it, you can be sure it works.

With an auto in a fuel injected car, it will help. In neutral, there is less load on the engine, so it can throttle back and feed less fuel to maintain the same idle RPM. With a carb, the difference is minimal, as the throttle is basically unchanged, just the RPMs due to load.

Hey guys, my first post here as this discussion has been interesting. But on the carburated car even though the idle speed remained the same, wouldn't the "load" cause more vacuum thus causing more fuel to be sucked out of the carb at idle?

Brian

Cool thanks everyone for the input I'll keep doin it even if it's minimal it still CAN help the environment and save a little gas Might i suggest you guys try it too?

Yep. :rolleyes:

Lucky you. I assume you don't do severe condition driving (all city, with lots of stop & go in heavy traffic.)


As fluid ages, it starts to break down. I prefer to change it often and keep it clean. From what you said I gather that you never clean out the pan and filter, either. If you ever do, it may change your mind...

"Beat the hell out of them" usually refers to worse than city driving. In fact, city driving is a picnic compared to the things I've done with auto transmissions.

I'm well aware of what happens to fluid, as well, and your preference is noted, and not under debate here.

I've cleaned pans and replaced filters, at the same times I change fluid.

If I change the fluid, it's a pan drop, filter change, and TC drain/removal. I literally change ALL the fluid at once, clean the pan, and inspect the transmission valve body for signs of damage/wear.

In fact, my wife's L200 (2001 Saturn) had 237k on it when we bought it, and NEVER had the transmission fliud or filter changed in it. I bought it from the original owner with a bad timing chain, replaced the engine, changed the filter and fluid, cleaned the pan, and all's well. This car doesn't have a dipstick for the transmission fluid. You're not supposed to change it. Ever.

When I cleaned the pan, after 237k miles, there was nothing in the pan. Pinkish fluid, and not even enough metal shavings to actually cover the 1" square magnet in the pan (OE installed).

This is basically the experience I've had with almost all the transmissions that, by your maintenance schedule, would be considered "severely neglected".

I feel the same way about it when people still insist on changing oil at 3,000 miles, as well, so it's not just you.

You just cited the #1 reason why I seriously considered but didn't buy a Saturn. IMHO, it doesn't have a dipstick because it's cheaper for them to omit it - and far tougher to check or change the fluid without it.

If "pinkish fluid" doesn't bother you, then I need say no more. I've seen discolored fluid and particles in pans at 30k miles. (But on your dipstick-less Saturn, there's no way you could know the condition of the fluid.)

Maybe not "neglected", but with no dipstick it's "out of sight, out of mind".

Oh, I'm "worse" than that. I change engine oil at 3 months and filter every 6 months, regardless of mileage. After having a few engines succumb to sludge due to 'severe condition' use I learned that frequent oil changes are an inexpensive precaution.

"An ounce of prevention is worth..."

The OE fluid is "pinkish" to begin with. So were the 15 bottles of Dexron VI synthetic fluid I had to buy because I made a stupid mistake and turned the engine off before replacing the check plug.

As much as the faith you place in it.

My daily route is close to 50 traffic lights. On a good day I will catch less than 5 red, sometimes only 1. On a bad day it will be close to ten.

I know the timing of almost every light, except for the recently installed ones that are not coordinated with the rest. I also know which traffic moving in the intersection indicates my light is about to change green.

People fly by me because I slow down a long way before the light. My goal is to go through the intersection with the least change in speed.

One stretch of 3 miles is 12 lights, and if I average 47 MPH (45 zone) I can get through almost every one of those lights, and even catch a 7 second green left turn only at an intersection where the whole sequence takes almost 90 seconds.

If I go 3 MPH slower I will hit yellow lights and eventually have to stop.

Since the CVT in the Insight cost 5k to replace and is not rebuild able, I pay $80 to change the fluid at the Honda dealer. It only takes just less than 3 quarts and has no converter to drain, so it's cheap insurance for me.


regards
Mech