synthetic in e30?

[nando]

bearing spec are ALWAYS make with a certain oil weight in mind check out the machinist handbook 2nd ed. and it will be in there. You are giving up power with thicker oil.

you know it's funny that people always talk about how newer engines have tighter clearances, but I'm not sure where they mean, there isn't a whole lot to the M20. the main and rod bearing bearing clearance on an M20 is exactly the same as it is on an M50 or S50, which supposedly have tighter clearances somewhere.

[JuanPabloBongto]

Amsoil Synthetic 5w30 for my 325ix (winter-only). I live in the tundra of Minneapolis.

[E30 Wagen]

you know it's funny that people always talk about how newer engines have tighter clearances, but I'm not sure where they mean, there isn't a whole lot to the M20. the main and rod bearing bearing clearance on an M20 is exactly the same as it is on an M50 or S50, which supposedly have tighter clearances somewhere.

+1

seriously, synthetic is good for any engine. Amsoil is good shit, and some 'synthetic' aren't even 100% synthetic, or so i read when i researched oil for a class project. If you ask me, it's a pretty interesting topic. I ran Castrol Syntec 5/10w-40 in winter, 10/15w-40 in summer on a 125,000 mile eta engine. Engine ran great, quiet, didn't consume, or leak oil for 3000+ miles and it still looked nice and clean at that.

However, dino oil is perfectly sufficient. I doubt it's really worth the extra cost so if you have been running dino oil, just stick with that if you're hesitant about spending more. I change a lot of oil where i work on a variety of cars/vans/trucks with 200,000+ miles that have been running dino oil and no issues so far...

[rThor432]

Nando's right about the tolerances. The bottom end of an M20 is extremely similar to the M/S5x motors. I see no problem with running synthetic, at all.

That said I run 15w50 in the summer and a blend of 5w30 and 10w40 in the winter. All synthetic Mobile 1.

[DaveSmed]

you know it's funny that people always talk about how newer engines have tighter clearances, but I'm not sure where they mean, there isn't a whole lot to the M20. the main and rod bearing bearing clearance on an M20 is exactly the same as it is on an M50 or S50, which supposedly have tighter clearances somewhere.

They have tighter clearances in many places. The bottom end isn't nearly as sensitive to oil weight as the top end is. Clearances in hydraulic tappets as found in the 24v engines are very tight and are spec'd for certain bleed down rates with a given weight of oil at given temperatures. That's not even getting into VANOS and it's particulars.

These engines also have a crankcase ventilation system that makes the M20's look ancient, allowing better oil vapor control.



I'm not going NEAR the synthetic debate, just remember 305°F...

[nando]

They have tighter clearances in many places. The bottom end isn't nearly as sensitive to oil weight as the top end is. Clearances in hydraulic tappets as found in the 24v engines are very tight and are spec'd for certain bleed down rates with a given weight of oil at given temperatures. That's not even getting into VANOS and it's particulars.

These engines also have a crankcase ventilation system that makes the M20's look ancient, allowing better oil vapor control.



I'm not going NEAR the synthetic debate, just remember 305°F...

that's fine, but it still doesn't fit with the "M20s have sloppy tolerances so run grease instead of oil" theories. The M20 head is incredibly simple, the only real tolerances there are in the cam bearings. :p

[a_thomasmr23]

i'm a fan of synthetic as well dont get me wrong. I also believe that its good for every engine. OEM's most often don't want to use because image buy a couple thousand gallons at the cost difference between syn and dino, ouch right.

+1 to DaveSmed

[DaveSmed]

that's fine, but it still doesn't fit with the "M20s have sloppy tolerances so run grease instead of oil" theories. The M20 head is incredibly simple, the only real tolerances there are in the cam bearings. :p

Correct, the thicker oil protects the engine better. The M20 is still saddled with a bit of a hold over of some ancient technology. The hardest place on oil in an M20 (and any engine so equipped) is the distributor gear. Even if you have an updated Motronic equipped car, you still have the distributor gear driving the oil pump.

You have to think of it as the M20 gets to use the better oil and doesn't have to compromise for the benefit of the engines hydraulics. The thicker oil will generate a much better hydrodynamic "wedge" between the shaft and bearing. Also notice the older engines seem to last longer.

Emissions really did it. Thinner oil (with the appropriate PCV system) is better emissions wise. Smaller piston skirts, better for emissions (lighter, but less durable) Ring lands closer to the top of the piston, same thing. etc.

The worst oil related thing was when they took the zinc out. Older engines (mainly domestic) started eating through cams. Many muscle car guys have taken to running diesel grade oil, as it (for now) still has the zinc. Interestingly, diesel oil is typically 15W40. I ran this in my M20s, and my Caddy.

The only real benefit to a thinner oil in an M20 would be better cold start properties, and less windage losses. Not better protection. The cold start in an M20 isn't too bad, the oil pump and passages are of a decent enough capacity.

In fact... many people notice increased oil consumption with thinner oil. I wonder how much of that would be eliminated if someone added a clyclonic seperator, maintaining the closed system. (catch cans don't count, most are atmosphere vented. They turn your PCV into a CV)

[xcmorgan50]

Ok this shit is confusing. I use castrol gtx 5w30 in the winter, 10W30 in the summer...simple. I've got 180,000 on the clock and I've never had to add oil in between oil changes or had any other engine problems.

[dlmpsy]

208K, conventional oil 'till 38K, synthetic since then. No problems.

[mikekristine325ic]

I run Conventional Valvoline 20w50. My car has approx. 335,000 miles with approx. 12,000 on a rebuilt head. I still have great oil pressure and don't burn any oil at all. When I ran 10w30, I had lots of valve chatter and went through a quart of oil in 3 weeks. The weather where I live gets down to 32 in the winter and as hot as 110 in the summer. Never had a problem running 20w50 so far.

If you can afford the price, I would run Royal Purple 20w50. My Dad ran this in both his tuned powerstroke as well as his 900hp '68 Chevelle. He absolutely loves Royal Purple.