jonnyyaa

I find my 2015 idles and starts up roughly. It has 50000km on it. I hope the carb cleaner helps - has anyone else put in a bottle or 2 and noticed positive changes (smoothness, power, mpg etc)

olgzr

I put in a bottle every year or two but see no difference in the way the car runs. It always runs and starts smoothly. Many years ago, before top tier fuels were invented and when I couldn’t afford the better brands of fuel, the carb cleaners made a huge difference in the way the cars ran. Not so much any more, but I no longer buy the cheapest fuel I can find, I stick to the top tier fuels.

The G Man

That's a smart move, a bit of preventative maintenance is better than damage control after the damage has been done. I hope none of you guys are using low octane non top tier gas, that could be another source of carbon build up. The quality of gas in the US is already really bad, to buy the cheapest low octane US gas is like buying the worst gas source and taking it from the bottom of the barrel.

Moisture

Typical driving styles sure don't help the matter either, which would include:

-Excessive idling
-Short distance trips (when the engine is cold)
-Constantly staying on boost (huge waste of fuel)
-City driving
-Never revving the engine out at all
- Stop and go traffic

Moisture

Maybe some on a high mileage car would help, but i would not bother.

jimbug

I have a 111,000 mile 2015 NX200t and haven’t noticed any sluggishness. It’s my daughter’s daily driver. She drives 45 minutes to work each day @ 55mph mostly, uses 91 octane gas, has a lead foot, so maybe not the best candidate for carbon build up. Hoping to get it to 200,000+ miles before the CPO warranty expires.

The G Man

The 45 minute drive each day would burn off some of the carbon. Every engine will have some carbon build up, just like all things mechanical, there will be some outliners out there that will exhibit some carbon build sluggishness. If it is not wide spread, then there is no carbon build up problem.

Moisture

Maybe. The intake ports need to reach a certain temperature for carbon to burn off, which will only happen if you rev the engine close to redline maybe 3 times within a few minute period or so.

E46CT

Engineering explained did a video on this a while ago. Yes heat is good for carbon mitigation but the truth is unless you're a full time hardcore race track driver, you won't see temps hot enough to effectively burn off carbon. Long story made short is there's not much you can do but drive. If it builds it builds. Any form of direct injection will still present problems later on.

Moisture

Generally speaking as long as you avoid short distance trips and driving around with a cold engine as much as possible and change your oil very often (more than 5000 miles...) You're not going to experience much buildup.

0w20 has been proven to cause extra blowby (and carbon buildup) so as long as you avoid using it, I think the intake ports will look clean well past 60k miles.

olgzr

If 0-20W oil has been proven to cause extra blow by, then our car should show some oil consumption between the 5K oil changes but there is no consumption in our engine. We currently have just over 40K miles on the car and the oil on the dip stick is at the same spot just before an oil change as it was just after the previous oil change.

Moisture

You are correct.

However - When I was over at the Mazda forums some guy had an oil catch can installed on his CX-5 and noted that it caught almost 500ml of blow-by after a 5000 mile interval. Another 5000 mile interval using 5w30 and the catch can was dry as a bone.

Just because you don't note any oil consumption, does not mean that carbon build-up isn't happening inside the engine.

I am willing to bet that using 5w40 oil will result in almost zero buildup on those intake ports especially considering these engines use port injection as well which should in itself remove most of the deposits. In my Mazda 6 the engineers rerouted the coolant passages away from the intake ports so that a certain amount of hard driving will get the ports hot enough to burn away any excess carbon.

The G Man

Its a double edge sword, the thicker oil will have a bit less blow by due to the larger molecules but the draw back is the larger molecules cannot get into the tighter space. Some space where it used to get lubrication can no longer be reach with the thicker oil. In my opinion, engine design is the biggest factor in carbon build up. Other factors that comes into play is driving habit, driving environment, type of gas used, gas octane and oil viscosity.

Moisture

Lexus states up to 20w50 is OK in some markets, while other markets mention up to 10w40. To be safe, lets say that 10w40 is the upper limit of what would be reasonable. That's not anywhere near thick enough to cause you the slightest issue with lubricity. I'm not sure you realize just how thick you would have to go to actually cause issues with clearances in your engine. Even then, unless it's well below freezing outside and you're not garage parked you wouldn't have anything to worry about.

I am not saying everybody should go out and put 20w50 into their engines, because there is zero benefit in doing so unless you're dealing with fairly significant engine damage and oil consumption, but do keep in mind that the turbo and timing chain puts an absurd amount of stress onto your oil supply, and not just 0w20, which, on my opinion isn't up to the task of protecting such an engine design; but really any average 5w30 oil isn't going to do much for more than a few thousand miles.

This I can 100% agree with.

The G Man

I agree, a slightly thicker oil is not going to make much difference one way or the other, The thicker has higher film strength and lubricate better at higher temperature. Does anyone know what is the typical oil temperature in the NX? If Lexus can manage to keep the oil at a reasonable temperature, it might be fine with the thinner oil. This is another case of car manufacturer keep pushing the envelope of using thinner oil to increase fuel efficiency, sooner or later, there will be a point where the oil become too thin.