5w-40 weight oil ... dumb question

[Powerzen2002]

My car is a 90 (240sx) with 75,000 miles.

I have a slow leak in my valve seals that cause me to burn oil
at higher rpms. ANYWAY, I normally use 10w-40 ... engine holds oil a hell of a lot long than with 10w-30.

I dont like the way the car drives on 10w-40, (feels sluggish).
Would 5w-40 be any better? Or is my mileage to high and car to old for the higher volisity of the 5w oil.

I know they say that 5w-30 is great for these cars (and many new cars .. ) but i dont think so on a 12-13 yr old car.

P.S. anybody know a good mechanic who works cheap and will be willing to fix my valve seals at a good price? hehe :)


Thanks!

[240 2NR]

That milage isn't very high at all. I have a 93 that's about to roll 70k miles and it runs fine on full synthetic 5W-30. I'd consider 150k to be the start of high mileage if well cared for.

Now my understanding is that the low number is it's cold performance and the high number is it's hot performance (viscosity). Going to a 5W-40 from 10W40 should only be a "lighter" weight oil when cold, but should act the same as your 10W-40 once up to temp. I don't think you will find a significant change in perforamance, all these weights are close. I believe tnord runs something like 15W-50 in his 240. My guess is the sluggishness is either from overfilling or another problem entirely. I don't think just a 40 weight oil would do it.

[AKADriver]

5W-40 is a bad idea for any car. To get the wide spread in viscosity, they need to use a lot of polymers that can gum up the works eventually, so to speak.

[Powerzen2002]

Oh. Ok, so what do you guys suggest?

Keeping in mind that I have 70K miles.
And, I have a little bit of a leak from my valve seals,
(which anything below 10w-40 allows the oil to
pass through the seals to easily and burn).

Any ideas???

[AKADriver]

You should find out why you have such an oil burning problem so early.

My 1990 has double the mileage of yours with absolutely no oil-burning issues. The engine's never been opened up in the time that I or the previous owner owned it. Something's definitely not right.

Aside from that your choices seem pretty clear... run 10W-40 and deal with a sluggish engine, or run 5W-30 or 10W-30 and deal with oil loss.

[S13wannabe]

the w means warm......so 5w-30 means it's 30 weight when cold, and 5 when warm. If you run 5 or 10w-40, you probably only notice sluggishness during start up and when it's cold. The good thing about high viscosity oils is that the oil stays at the top of the engine longer. Are you sure it's valve related ? It sounds to me more like rings, if you're burning oil, but less with higher viscosity oils. You need to do a compression check, first and foremost. That will tell you a lot right there. If it's your rings, you obviously have no choice but to replace them in order to quit losing and burning oil. If you don't have the money to replace them right now, run the higher viscosity oil like you are now, or add some Engine Restore, or Engine Honey. But that only helps slow down the oil loss. If you end up needing new rings, and you do it yourself, replace the main bearings while you're at it. They are cheap, and it will be well worth it later down the road.

Good luck,
Mike

[SRKperformance]

bring the car by my place and ill check it out, ill run a full diagnostic for 20 bucks, ill do a leak down test also. ITs prolly not valve seals. valves seals leak when the engine is cold or at low rpms. What is the history of the car? has nos ever been used, did you buy it from a grandma or a street racer? High rpms spells worn rings normally possibly from overreving or too much nos. A leak down would clear everything up. Then if it is somthing like valves or the head itself we could get a whole new head for the price of doing the valve job. well see. Also is the smoke bluish white, just whitish grey , is it sweet smelling, or nasty, or gassy?

[SRKperformance]

also if higher grade oil is making things better it again sounds like an oil pressure problem possibly the rings or ring lands. If no smoke gets rid of the problem it could be some sort of internal oil leak thats getting into your combustion chamber.

[240 2NR]

Multiweight oils and polymers explained (http://www.repairfaq.org/filipg/AUTO/F_oil_facts.html)

W means that an oil has been designated as suitable for winter use by the SAE

Example 10W-40
The first number (in this case the 10) describes it's viscosity when cold

The second number represents it's warm viscosity

But I do agree that the further you spread the weights the worse it is for the car under load once warm due to the higher concentration of polymers. At the same time a lower cold weight helps save your started by reducing the work it must do in pumping the cold oil.

[Powerzen2002]

SRK Performance .... I WISH I COULD bring it down! BUT, I
dont think driving it across the country is a good idea! :)

I am in New York.

Ok, here is the deal no that oil problem.
Regaurdless if the car is hot or cold, if I put the car in neutral
and open the throttle full blast, I get a blue'ish smoke from the
exhaust.

I bought the car with only 48K last year from a older woman,
she was the only owner. She did the normal maintanance,
I checked it out.. never an accident.

At around 65K the oil problem appeared out of no where.

If I am driving, at WOT on the expressway I get can see the
smoke if I REALLY launch the car. Otherwise, I never see the
smoke.

[SRKperformance]

wierd, try chekcing your sparkplugs. To see which cylinder is burning more oil, then you should go down to your local auto parts store and buy a compression tester they are like 30 bucks for a cheap one. Crank the thing 6 times for each cylinder one by one with all of the spark plugs out of each cylinder and record the psi shown on the compression testers gauge. If you can have a friend help you by cranking while you watch the gauge and hold it. after he finishes cranking watch and see if the gauge holds the psi steady for a while or if it slowly drops. If it slowly drops its prolly the valve seals. IF when cranking it (during the cranking) the needle jumps up falls down slightly and then jumps up between each crank its almost definitly valve seals because as each intake valve opens they do not seal all the way allowing some pressure to leak out. The pressure should be around 170 psi for a ka24de, and 160 for ka24e and each piston should be about 5-7 psi within each other in terms of the readings consistancy.

[sxtasy]

Originally posted by S13wannabe
the w means warm......

He He He, That was funny! The wide range of viscosity is due to a synthetic oil wich is engineered to provide a wide range of protection, not from polymers, pixie dust, or anything else. And if you can tell a difference in drivabilty in 10 viscosity points you must be magic. This thread is funny :D

[240 2NR]

Did you read the link I provided? Does anyone read any of the links I provide?

Synthetics allow for multiweight oils without polymers, however in a convention oil these are present and represent cause for concern running more than 30 points difference as it tends to indicate more additives. Additives do not lubricate so the more that are included the less oil there is.

[silvia lover]

well. you saw the blue smoke while it's full thottle, it's sounds like you running rich to me(don't flame on me if i was wrong :p ), you should check it out and see will it fix it(sorry, forgot what you have to look for :( ) hope it's help

[AKADriver]

wrong.

blue = oil
black = excess fuel
white = coolant

[Powerzen2002]

No its blue smoke like I said, ... and there is no two ways about
it beacuse I burn half a quart of oil every week and half.

Damn valve seals!