Oil Changes To Reduce Blow-By ? Recommendations.

[JSRT4]

I know excessive blow-by is a mechanical issue with any given engine, and a repair is in order to ultimately correct it. My car runs great and I am not about to open up the engine because of it. But can changing oil viscosity help ?.

I was at the dyno on the other day and towards the last 500 rpms before redline my oil dipstick was popping out of its hole. My car is a 2002 Honda S2000, redline is 8900 rpms. The dipstick does not pop out at any other time other than the very top end of the rpm band. I am currently running Castrol Edge 10w30 oil. The O-rings on the dipstick are not worn, but I could look at putting on some thicker O-rings or a hold-down strap on the dipstick.

Looking at alternative oils I am thinking of trying Redline 5w40 or Amsoil 0w40. Any chance either of these oils could reduce Blow-by on my engine ? 5w40 is a recommended oil weight within manufacturer's recommended range, along with 10w30.

Thanks for any opinions on this.

Joey

 

[simple_gifts]

Is there a PCV valve?

 

[JSRT4]

Yes a factor pcv valve, which is in good condition. I run the line off the pcv valve to a single catch can and then run a line back to the intake manifold. I don't think that has any bearing on the issue as the dipstick pops up under WOT conditions and very high rpms when the pcv valve wouldn't normally have much vacuum. There is a relief port that goes to the intake tube at the front of the valve cover too.

 

[Quest]

+1 with simple_gifts.

Unless you have modified your engine, otherwise: there should be a PCV valve that would create an overall negative pressure (PCV on NA engine will draw crankcase fumes into intake manifold, and the other end of the PCV system is open-ended (draw fresh are from the intake manifold).

If you pop your dipstick, then there's excessive crankcase pressure...start looking somewhere along for answer.

Q.

 

[Shannow]

some viscosity/engine/wear combinations cause some strange piston ring dynamics that can massively increase blowby/consumption.

Try an A3/B4 10W30 (M1 Hi mileage is 3.5HTS IIRC) before you go to a 40.

0W, 5W40s only get you to an HTHS of 3.7/3.8, whereas for a dyno run, a 15W40 could get you into the 4s.

 

[Brybo86]

Try removing your custom catch can and revert to OEM PC setup.

See if it still pops off

If it doesnt... There's your answer.

 

[JSRT4]

Thanks for the reply, I'll test out the pcv system and make sure I am getting proper suction (negative pressure), but I think the pcv system has very little suction at WOT. My engine setup is pretty much stock other than the oil catch can.

 

[JSRT4]

That's interesting, thanks for the info on HTHS changes, I may go that route if it can help.

 

[JSRT4]

Thanks , yeah I could easily revert the piping back to stock and see if it changes anything, my catch can setup hasn't been on very long. Thanks for the tip.

 

[JSRT4]

I should also note that this motor runs pig rich at the last 1000 rpms of the rpm band - 8000-9000 rpms, probably making the blow-by worse ?

 

[CBR.worm]

In addition to the pcv valve, there should be a fresh air intake going into the other end (typically) of the valve cover from the clean side of the air filter after the MAF. If this is plugged for some reason, pressure could build and the dipstick could pop out. The pcv valve doesn't typically flow very much. My impression is that the only reason it is a check valve is to prevent backfires from entering the crankcase. If the pcv valve was sealed shut, pressure still should not be able to build in the crankcase. The PCV system requires fresh air flow to carry the blow by [censored] out of the motor.

There are some exceptions - notably a couple German cars, but Honda stuff is usually pretty straight forward. If your car was turbo'd, you might need to move the fresh air source to a different location to prevent boosting the crankcase.

 

[JSRT4]

Originally Posted By: CBR.worm
In addition to the pcv valve, there should be a fresh air intake going into the other end (typically) of the valve cover from the clean side of the air filter after the MAF. If this is plugged for some reason, pressure could build and the dipstick could pop out. The pcv valve doesn't typically flow very much. My impression is that the only reason it is a check valve is to prevent backfires from entering the crankcase. If the pcv valve was sealed shut, pressure still should not be able to build in the crankcase. The PCV system requires fresh air flow to carry the blow by [censored] out of the motor.

There are some exceptions - notably a couple German cars, but Honda stuff is usually pretty straight forward. If your car was turbo'd, you might need to move the fresh air source to a different location to prevent boosting the crankcase.


yup all of that factory setup is in place, nothing blocked, though you would think that the front opening would allow pressure to bleed off if needed. The pcv doesn't flow much and at WOT I think vacuum is very low on the pcv.

 

[Ducked]

Pending diagnosis/repair, you could perhaps replace the dipstick with a filter or a hose to the intake tract (after the air filter), depending on the level of your environmental concern.

A filter might get oil-soaked pretty quickly though.

 

[TFB1]

Originally Posted By: JSRT4
Thanks for the reply, I'll test out the pcv system and make sure I am getting proper suction (negative pressure), but I think the pcv system has very little suction at WOT. My engine setup is pretty much stock other than the oil catch can.

You are correct the PCV system have zero negative pressure at WOT, never seen anything fix this condition but a tie down... I own a summer driver that will push out the stick at high RPM, hooked a spring to it about 15 years ago, been fine since...

 

[BrocLuno]

If it's ring dynamics at WOT at high RPM (ring flutter) a change in viscosity might do it...

You'll be experimenting anyway, so don't creep up on it. Just go to Delo400 15W-40 and see what happens? If that helps, yeah. You can now start backing down to lighter weights. If not, you'll know that oil won't do it and you need a to use a mechanical solution...

 

[JSRT4]

Originally Posted By: TFB1
Originally Posted By: JSRT4
Thanks for the reply, I'll test out the pcv system and make sure I am getting proper suction (negative pressure), but I think the pcv system has very little suction at WOT. My engine setup is pretty much stock other than the oil catch can.

You are correct the PCV system have zero negative pressure at WOT, never seen anything fix this condition but a tie down... I own a summer driver that will push out the stick at high RPM, hooked a spring to it about 15 years ago, been fine since...


That should be easy to do if I can find the right sized spring, a 15 year fix would do me just fine , lol

 

[JSRT4]

Originally Posted By: BrocLuno
If it's ring dynamics at WOT at high RPM (ring flutter) a change in viscosity might do it...

You'll be experimenting anyway, so don't creep up on it. Just go to Delo400 15W-40 and see what happens? If that helps, yeah. You can now start backing down to lighter weights. If not, you'll know that oil won't do it and you need a to use a mechanical solution...


Thanks , that would be a cheap test, and quick enough to do too. Ring flutter does make sense, as it happens at such a short point in the upper rpm band.

 

[turtlevette]

With my t/a I put an extra vent where the oil cap was. This prevents positive crankcase pressure from blowing oil out the rear main. You want to vent things not plug them up.

 

[Ducked]

Originally Posted By: turtlevette
With my t/a I put an extra vent where the oil cap was. This prevents positive crankcase pressure from blowing oil out the rear main. You want to vent things not plug them up.



Check

 

[JSRT4]

I recently put in Castrol Edge 5w40 for my end of season drain and fill. I took it out for a few runs and the dipstick has not popped up since, ran the engine up to 9000 rpms a few times and the dipstick has been okay. I'm hoping this has reduced the amount of blow-by. All else has been kept equal. My previous fill was Castrol Edge 10w30, where the dipstick was pushing upwards at high rpms.