Best way to reduce blowby? 15W-40 or synthetic? Or motor honey?

Or, fixing the engine problem causing blowby.

If you are running a diesel, and you are on a diesel forum so I'll assume that is the case, you should already be using a 40 weight oil. The number that matters once the engine is warm is the last number. If your blow by is excessive with 40 weight oil, the next step is a 50 weight oil. It can be hard to find diesel ratings on say a 20W50, but there are some out there. Mobil 1 has a 15W50 with a diesel rating. The Motor Honey approach will work, but you have no idea what your oil viscosity is after adding a bottle, so I would try the higher viscosity formulations first.

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'97 E 300 D

that's a brilliant idea! why don't you come on over and fix it for me in a jiffy on my gravel driveway in the 90 degree heat with the black flies, my 2 kids climbing all over you and my wife b******* at you for not playing with 2 kids or paying attention to her. Or you could take it to your shop and wave your magic wand.

I've had the car about 3 months and haven't driven it much. . I have a couple gallons of Valvoline 15 w 40 diesel formulation.

I'm going to reply to my own post and call myself a dumbass .
I will first change the oil with 15 w 40 can take it from there .

Is this a hypothetical question? Is there a particular car you have in mind? What are the symptoms that lead you to believe there is a blowby problem? Is the crankcase ventilation system working properly?

Sixto
87 300D

I have an even better idea why don't I just go and buy a brand spanking new 2012 mb diesel from the stealership.

85 300d. High miles. Smoke wisps from fill cap anid vent tube to filter. car has great power though.

They kinda all do that. How much does the oil filler cap rattle if you set it lightly over the oil filler hole?

Sixto
87 300D

If your Blow-by is being caused or increased due to sticking Piston Rings Synthetic Motor Oil might decrease the Blow-by. But, I think there is only a small chance of that working.

There is at least several thread on ways to route the Blow-by out of the Air Filter Housing so that it does not contaminate your Air filter.

If you are going to try something like Motor Honey in your Oil you should use single Viscosity Oil because part of what that stuff does is increase the Viscosity of the Oil. I don't think it is a good idea to put it into Multiviscosity Oil because it messes with the multiviscosity part.

I have also seen on a Diesel Generator set where increasing the Oil Viscosity also increased the Oil Consumption.

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84 300D, 82 Volvo 244Gl Diesel

Sticking piston rings..... Can I fix that with some atf in the oil for anout 5 miles before oil change?

Oils wisps from oil fill and vent tube when it gets warmed up. And high miles

You mean oil smoke, right? If it's wisping, that's normal, check that I should say that is GOOD if the car has more than 200k miles. Having some smoke is normal as the motor ages.

Blowby isn't wisps... it's smoke under pressure shooting out when you pull the oil cap, accompanied by a light shower of oil droplets in the vicinity of the fill opening if it's serious.

As long as the car performs okay, blowby is a Feature not a Problem

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

This is as good as it gets

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250, Dec 2024 145,000 miles