Foaming & Ester Oil Concerns in 1990 Ferrari 348 with Cam Seal Leak

[altaylar]

Hi all,


Looking for some input on oil choice for an older car with a light cam seal or gasket leak. The previous owner used Red Line 5W-40, but I’ve recently read that ester-based oils can sometimes aggravate seal issues in older engines, even though esters are supposed to be good for the seals, unlike PAI. Have others here experienced this?


To be cautious, I switched to Mobil 1 10W-40 High Mileage for its high ZDDP and seal conditioners. After a short 3-minute run just to check the oil level, I noticed significant foaming on the dipstick.


Could this be:

• Normal behavior during the first few minutes of running?
• Caused by mixing with leftover Red Line?
• A known issue with Mobil 1 HM?

I’ve seen other members report foaming even with Pennzoil Euro L 5W-40, which is manufacturer-recommended in some cases, so I’m not sure how much to worry.


I also have Motul 300V 5W-40 on hand (which I use in my track car), but I’m hesitant to run another ester-heavy oil until I better understand seal impact.


Any insights appreciated—especially on early foaming and ester compatibility with older engines.


Thanks!

PS: How long does it usually take for the HM oil's seal conditioners to do their work? Should that be noticable immediately?

 

[facility1]

switch back to Red Line 5w-40. its perhaps a better oil in this case or . Amsoil EFM makes a fine 5w-40 to add to this situation.

 

[Jetronic]

Red Line oils tend to have more anti-foaming additive in them (basically a splash of silicone oil) than you typically see. I don't know if that's because it needs it, or they want to reduce foaming below average.

If an oil is prone to foaming, it'll likely be worse when the oil is cold.

I don't remember anyone developing, or worsening leaks by using Red Line or other PAO/ester oils. I also don't remember seeing it solve leaks either.