How much zinc "zddp" in Mercury 25w40 oil?

[Phil_clark]

I have an older boat with a Merc 165hp in it and this year was researching oil to use and been going crazy!! Years past I have used straight 30 or 40 weights and last couple years used Mobil 10w40 full synthetic. This spring I just put in some Rotella HDEO 15w40 after hearing good things about it. Then I started reading how the new API rated oils have reduced zinc zddp levels which can harm older motors. So I bought some ZDDPlus additive to bring up levels. Now my question is do the marine oils like 25w40 still have higher zinc levels in them? I have looked all over internet and can't find answer to that. I sent email to mercury marine and got this response:

Thank you for your interest in the MerCruiser product. Regrettably we do not have a chart that would indicate what the ingredients or the amount of each ingredient is in our lubricants. MerCruiser does not have guidelines that would give us indications of safe or unsafe levels of additives or contaminants. We do not base our decisions of engine health on oil analysis.

 

[ledslinger]

ZDDP levels are critical for fast opening performance cams with stiff valve springs. Your engine has a mild cam that doesn't need stiff springs. Your engine would be fine with SL/SM oils.

HDEO will likely protect your engine better than any oil that was available when your boat was made. HDEO in 30, 40, 10-30, or 15-40 will be fine for your engine.

Welcome to the forum.

 

[ARCOgraphite]

Is this a Chevy 305? Run john deere +50 or TorqGuard in a 15-40 wt if you tend to run wide open a lot; the 10w-30 will work fine if you use less throttle and RPM but will easily hold up for brief 10-20 second full throttle runs. They all have "enough" zddp - its more critical in fresh engines than those well broken in.Pennzoil also has marine oil - but any good HDEO will work fine - Folks love 5w-40 Rotella T6. Stay away from regular passenger car oils.

 

[Phil_clark]

Thanks for info, it eases my mind. I have a 1974 250 inline 6 165 merc, great engine. I ususally run it around 3000 rpm and put on about 50 hours. The other thing I am worried about is the shear stability for example of the Rotella 15w40 I just put and others. If you read the marketing mercury does for their 25w40 and the full synthetic companies, they lead you to believe any other oils will shear fast in marine engine and lose viscosity? For couple years I was using Mobil 1 10w40, is it worth the extra expense? I already bought bottle of zddplus so guess I will sell it or use half bottle this year and half next. I don't want TOO much zddp either. Thanks

 

[Steve S]

Any over the counter HDEO oil has enough zinc without needing additives.

 

[ledslinger]

Phil- Mercruiser has to consider oils from the standpoint of the most severe conditions their engines COULD operate in. A cruiser that runs at 3/4 throttle all day would breakdown a passenger car oil. Few pleasure boaters place such demands on their boats, and don't require oils that stand up to this. Most users rarely run full throttle, and if they do it is only for a short burst.

Their specs have caused you needless worry and it sounds like you have taken great care to use oils that won't cause problems. Use an HDEO and relax.

 

[dwendt44]

The inline 6 cyl. MercCruiser is a Chevy I-six of the same year as the Merc.

 

[ARCOgraphite]

The mobil 1 10w-40 would not be my #1 choice. This kind of syn will not do anything beneficial for your boat. I say again JD Torq-guard or RT5 10w-30 should do fine.

 

[friendly_jacek]

I have the Merc 135 and according to my research, HDEO 15W40 like your rotella is the best thing you can do in this or similar application after the break in is complete. I also have and use "marine" 15W40 oil I picked up on clearance, but suspect it's re-bottled HDEO 15W40.

I used to use 5W40 synth rotella one season, but it did not make sense for 2 reasons. You do not want to do extended OCI due to contamination and HTHS of 5W40 is lower (~3.5) compared to 15W40 (~4).

I used the genuine 25W40 Merc oil for engine break in though. The merc oil has much higher ZDDP (~1600) compared to HDEO (~1200) based on posted UOA and VOA.

 

[BigCahuna]

When I had my inline six, I ran straight 30 or 40 wt Pennzoil. And a standard Purolater filter. The boat was a 1968 with who knows how many hours on it. I had it for 6 years and ran it about 60 -70 hour a season.No oil related problems, besides a minor oil pan leak, I always had 40 plus psi of pressure when running.I wouldn't run multi grade oil in a motor working that hard.

 

[Pete591]

Racing 40wt's..like Kendall/Castrol/Valvoline..etc work great.

Some guys like M-1 15W-50

M-1 V-Twin 20W-50 has about 1600 of ZDDP and is used a lot by high performance boaters. It would be my choice with a Wix oil filter.