Question about Oil Usage and RPM's while coasing in Neutral- Is this normal?

[blackntan]

2011 Mazda CX-9 Touring w/ 22k miles, bought new. No towing, just daily work commutes.

1st Question. Just checked the oil level the other day. I've got 3k miles on this fill of Mobil 1 5w-20 so far. Oil level was at the bottom of the marks. Added 1/2 quart topped it off. I'm absolutely certain when I did the oil change I filled it properly (5.5qts if I recall, don't have the manual handy right now). Do these things burn or lose oil? There are no leaks...under the hood and under the car is immaculate. IMO, 1/2 quart in 3k miles isn't a big deal, but it wasn't expected either. Just curious if this is something to be concerned about, otherwise I'll continue to monitor it. Have plenty of drive train warranty left if it turns out to be a problem. Also, I previously had been running German Castrol 0w-30 in the engine, and had 0 oil use or loss, IIRC. I just started back with 5w-20 on this past fill, and now I'm noticing some use/loss.

2nd Question. Transmission/Engine possible issue or normal? I've been driving the CX-9 a lot over the past couple weeks (my wife usually drives it) One of the things I sometimes do in my other vehicles to try to maximize MPG, is to shift to Neutral when coasting to a stop light. Every other vehicle I've done this in, the RPM's drop down to normal idle RPM range. On the CX-9, I've noticed that even after shifting to Neutral, the RPM's stay in the same range as if it thinks it is still in gear (like 1500rpm,then slowly decreases as the speed of the car decreases). Is that normal? I would expect the RPM to drop down to normal Idle RPM range, unless it is in gear, regardless of vehicle speed. Thanks.

 

[sts7049]

for question 1, i wouldn't be too concerned about 1/2 quart over 3k miles. some engines use a little. as long as you keep an eye on it and keep her full, keep on trucking.

 

[robertof]

When you put a car in neutral the AFR goes back to stoic, if you just let go of the gas the AFR is leaner since the injectors shut off. You actually uses less gas while letting go of the gas pedal than by putting the car in neutral.

 

[mazdadude]

When you put a car in neutral the AFR goes back to stoic, if you just let go of the gas the AFR is leaner since the injectors shut off. You actually uses less gas while letting go of the gas pedal than by putting the car in neutral.

(friday)

Exactly what robertof said...(2thumbs)

As far as the oil usage goes, I would continue to monitor it and make certain there is no excessive usage.

 

[blackntan]

Thanks. I'm still stumped though, why the RPM's stay high if I move it to neutral. Doesn't happen like that on any other vehicle I've driven, normally just goes down to idle RPM, like 500-600 or so, but the CX-9 stays at crusing RPM, like 1500 or whatever...weird.

 

[table5511]

Soon as I hit the motor warranty, I switched to 5/30 and have noticed less oil use than with 5/20. The 30 just lubricates better so my guess is that less is burned off i.e. this makes sense that 5/20 kills engines prematurely in exchange for trying to eeek out another penny worth of gas mileage.

 

[blackntan]

Soon as I hit the motor warranty, I switched to 5/30 and have noticed less oil use than with 5/20. The 30 just lubricates better so my guess is that less is burned off i.e. this makes sense that 5/20 kills engines prematurely in exchange for trying to eeek out another penny worth of gas mileage.

It's funny you mention that. I was running 0w-30 in the car from 10k miles to 19k miles. 0 oil was lost, from what I can remember. I only decided to switch to M1 5w-20 at 19k miles because I wasn't happy with he MPG the car was getting in town, and wanted to see if the thinner viscosity oil would give a little bump in the MPG...and it did. With the 0w-30, it was getting mid 15's to 16mpg. After switching to the 5w-20, it is getting mid to high 16mpgs, trying it's hardest to hit 17mpg. The road trip highway mpg with the 0w-30 was 22.20-24mpg, and with the 5w-20 was 24.10 and 24.20mpg, same destination. Not a huge enough increase, and not completely scientific, but there's still something there.

I agree that the 0w-30 probably lubricates and protects better than the 5w-20, but the manufacture calls for the 5w-20 for CAFE/mpg, and I'm sure they could care less if the engine lasts beyond 60k or 100k miles, but the consumer actually wants it to last 200k-300k.

Well...I'm not as concerned about the 1mpg difference anymore, because I have sold my gas guzzling truck (12mpg in town), and am driving a more fuel efficient car now (Camry). Therefore, the poor, 15.5-16'ish mpg that the CX-9 gets with 0w-30 will be just fine with me. Actually, my wife stole my car from me because she likes it so much, lol, and now I am driving her CX-9 these days

I think I'll go back to the German Castrol 0w-30 next oil change, which also happens to be the same exact oil I use in the V6 Camry, so I won't have to worry about having different kinds of oils around. I'm not concerned with engine warranty, the engine ain't gonna blow up because I use 0w-30....

UOA on 9k miles of GC 0w-30 showed a TBN of 4.3. I'll probably dump the M1 5w-20 at 7500 miles and start back with the GC 0w-30.