Boneknot

I found out last night that it is a bad idea to let your car "warm up" last night. It has been getting around 30 degrees at night here in North Carolina recently and I work night crew. Anyhow I had filled the car up the night before and let the car idle for a good 20 minutes to "warm her up" before i left work. My drive to work is only 4 miles to add to this. So in the 16 miles to work and back that i had put on and 2 "warm up" sessions, I used almost a quarter tank of gas. Has anyone else noticed that it seems to use alot of fuel if you let it idle for awhile? Just thought I would throw that one out there.

Golfer

20 minutes is a bit extreme IMHO. I believe the owners manual says 5 minutes, which is what I do when I drop the kids off to school - all of 2 miles stop and go from the house. I get about 15 MPG doing this.

my10ae

I too have noticed this. I bet it would go along with the fact the MPG is horrible. Half the gas consumption (SWAG) is used up in the warm-up process.

6speed8

Yes, this car absolutely hates idling, it uses a huge amount of fuel doing so. That's why the fuel mileage is really bad in city driving - it's because of idling at red lights.

Rotary Nut

Oh yeah I have seen this! I never let it sit more than a few minutes. You can almost hear "a great sucking sound" as it eats that gas!

f1michel

I think idling to warm up the car is a pure waste of money. Get in there, turn the key, buckle up and go ! I live in Mtl where it gets WAY below freezing and i never ever warm up a car. it is not good for the car, the air i breathe or my pocket. And frankly, 30 F is not that cold. :-)

pepe

Ummmm, anyone who's been in a rotary before should know about this phenomenon... :p there's posts on here somewhere explaining why, something about the internal surface area of a rotary engine or some such nonsense means when it's idling, it's still using a lot of fuel.

Mitch Strickler

I too read something about warmup, but couldn't find it when I reread the manual. It isn't there; it's in the little "Driving Tips" mini-brochure.
More important, it doesn't say to warm up the car five minutes before driving. It is only about those times when you want to start a cold engine and then only drive it a few yards -- for example, moving a cold car to a different slot in a parking lot. Instead of shutting it off after that few seconds of running, Mazda says to idle about five minutes and then rev to 3,000 for ten seconds.
The manual says that normal driving (when you're going to drive long enough to warm up the car before shutting it off) requires very little warmup. All the other manuals I've seen say the same thing, because the fastest way to warm up the engine, and therefore the best thing for the engine, is to drive with light throttle and low revs until the temp gets to normal.

Tamas

iTrader: (1)

Exactly as Mitch said.
There is NO need whatsoever to let this car idle for 20 minutes before driving away. Just get in, fire it up and go. Only thing is, don't rev it too much while cold. Keep it low until it warms up.
Folks, this is not some junky 30 years old russian Lada or romanian Dacia, for God's sake... the only thing you gotta be careful about is the cold shutdown, but even those "horror stories" are exaggerated on this forum. Yes, you CAN flood it - but just by exercising a little care, you should be fine and it certainly NEVER requires an excessive warmup or idle time.

RX-Nut

I usually warm it till the temp gauge starts moving to hit the C. That way if I F' up and stall the car by mistake I lessen the chance of a flood.

But yes, at idle or in traffic, I swear I can see the fuel meter drop and drop and drop.. hmm.

s1mike22

no need to "warm up" the car. as long as you don't stall, the driving process is basically your warm up.

Haze

It is actually better to run the car gently after start up than to let it idle. It lets less gas run around in the rotor unused than idling and the car will warm faster if running gently. Besides that, you are getting where you want to go. That's always good. Warming an engine by idle is a left over concept from carburetturs that would stall horribly if not warmed up, and even then the manufacturers would tell you to do it as little as possible because it dumped fuel into the cylinders and wore the cylinder wall as well as fouling the oil. Just drive the car gently the way the driving tips manual says to and all will be well.

Sin

I warm up 5 mins, seems I've gotten that from different people.

Boneknot

The only reason I wanted to warm it up is that the windows have been totally frozen over. Trust me after I learned about how bad it is on gas I am going to bite the bullet and just drive the sucker with fogged up windows until the defroster kicks in. Thanks for all the help though.

jdwk

Idling to warm up not good for any car. Suck it up and go, but just keep it under 3000 rpms until the temp gage is normal.

Turning the car off before then is also bad, because the oil is still viscous and can get trapped. At least that is what I read and it seems to make sense.

O.R.A.

While I agree that the best way to warm up the car is to drive it, it is not as simple as "just go". Even when the water temp gauge is at the "normal" level, the oil is still not warm. Cold oil makes the oil pressure be sky high and the higher you rev, the more work the oil pump has to do to move that cold thick oil through. Keeping the revs low for the first 5 or so minutes still lets you drive the car, but with as little stress to the oil pump and oil seals as possible.

jdwk

I agree, coolant warms faster than oil, but it is a fairly good gauge. And most cars don't have an oil temp gauge.

Racer X-8

5-20 oil is multi-viscosity, and the lightest weight for an engine that I know of. I'm not an authority on the renesis, but that is food for thought...it should perform like 5 weight oil when cold, which is very thin.

I don't idle to warm up an engine. Never have, unless letting her idle while clearing the windows counts. If / when the windows are clear, I go. I go without being agressive at all for a while, till it's pretty well warmed-up.

Idling a cold engine is bad due to the oil pump not being very efficient at idle & could "starve" some running surface which relies on a constant supply of oil for lubrication. Like the valve stem seals. :p

Naginata

One of my co-workers has a new Mach1 that takes 0-20 oil... so there IS lighter oil out there, somewhere

bobclevenger

I tend to agree with you. But where I live (condo complex) there is a 5 mph speed limit on the perimeter road (read: "big driveway") and of course I live about as far from the entrance/exit as you can get. If I try to drive out immediately after starting up (my former procedure) I get a "bucking bronco" ride as I try to hold down to 7 or 8 mph. I guess the ECU doesn't feed a decent mixture at that speed before the car warms up. So I have changed how I start out: I let the cold engine idle until the RPMs drop to 1500 from the 2000 that it starts at; then I pull out. This is only necessary if the car has been sitting overnight. This "warmup" period is only about a minute or so.

cruzdreamer

Wow, 20 mins.....too long to idle. I drive 10 miles and the gauge goes to the first hash mark from full......it bothers me cuz I am always checking my gas gauge! This car drinks fuel like crazy.....filling up every 3 days! I let it warm up like 2-3 minutes then drive....it hesitates a little till it fully warms up though.

Mitch Strickler

I have an early-build AT, 0717 VIN. I have never experienced bucking, stalling or the like, and I start and drive away (gently) as soon as the "RX8" on the screen is replaced by the time/temp/etc. display. If a car delivered 11/1, which was built after the US horsepower/economy shortfalls were well known, stumbles under those conditions, maybe it means that Mazda is now setting ECUs at less extremely rich mixtures. This is just a guess. Wishful thinking, really, because I hope Mazda has found more economical settings that still meet emissions laws, and will someday reflash ECUs with them, at least for those of us who keep complaining about gas guzzling.

bobclevenger

I think that is more a function of A/T vs. M/T than anything else. I think my 8 (bought 10-30-03) is very rich when first started -- you can hear the difference with the new exhaust when it warms up just a little.

Mitch Strickler

BobClevenger thinks my bad mileage may be caused by the AT. For a variety of reasons, I don't think this general rule, once true, applies to RX8s. Start with a big AT advantage, much higher gearing. Over the road, I'm running 23.5 mph/1000 rpm; the manual, only 19.4. And there's no slippage in fourth gear (or third). Point for AT in highway driving The lower-speed design of the AT's engine, without provision to pour in gas from extra passages and injectors at top revs, and with a bit more torque at slightly lower revs, should help a bit. The old automatic drawback of not being in the optimum gear at times is not applicable to the 8, where you can pick your own gear. (In fairness, I must admit that four speeds don't offer as many fits as 6.) For what it's worth, the AT scored 18-25 on EPA ratings, vs. 18-24 for MT.
Bottom line: Congratulations if you are getting something like the mileage you should with an MT. If my engine were built like the pre-production ones that did the EPA tests, I think I'd be doing a little better than you are.

RodsterinFL

Remember that the rotary is firing 3 times every revolution so the energy efficiency will disappear in an idle. It DOES generate more heat to keep warm though!!!

Bad mileage is relative too. The long term rap with the G35C at Edmunds indicated a real 17 MPG town on that car.