Going from conventional to Synthetic - Good or bad?

[Sevillian273]

Well thats good to hear! Ive decided against synthetic because of the risk of gasket issues and possible lifter noise like I had on my high mile mercury when i used synthetic blend in it. Not to mention the 26 bucks id lose if I had to go back to regular oil! So Ive got 6 quarts of Rotella in my back seat ready to go. Ill note my oil pressures as of now, and after the change to 15w-40 and Ill post the results if any...

[submariner409]

Google "knize oil filter study" for more than you'll ever want to know about every brand of oil filter made.

My 455 Olds boat engines run 8 quart pans and Melling HP oil pumps with Pennzoil 15W-40 Long Life truck oil and WIX filters. Normal oil pressure is 55 psi hot (oil @ 220 degrees, normal) at 2,200 rpm and ~20 psi at 650 idle in gear. The Melling bypass relief is set at 60 psi, and ports excess cold oil back to the pan. A modern GM engine generally runs around 40 - 45 psi hot with the recommended oil. Ford tends to run a few psi higher.

Unless your engine is very old and "loose", 15W-40 is too heavy for passenger car use. The engine below is built to run 15W-40 due to the loads it pushes (an 8-ton workboat, at 2,200 rpm, 8 hours a day, 6 days a week. The engine will go your car equivalent of 350,000 miles in its life, and will be overhauled to do it again. The block shown is a 1971 455 with roughly the equivalent of 1,300,000 miles and is on its third major overhaul and is still at +.040" on the Keith Black 9:1 pistons.)

If you are used to damped electrical gauges and idiot lights, watching an engine warm up and the attendant oil pressure changes is an eye-opener for some and a worry for others who never knew mechanical gauges. You would panic if you saw what an electric fan-cooled engine does in the temperature department !!

[Sevillian273]

Well Ive decided to go with some 5-30 conventional for the colder months. It will be a bit of an experiment to see if it causes any low pressure condition, which I doubt because it has low miles. I really dont like seeing such high pressures on cold mornings.... Even after It hits operating temp, The pressure still takes a while to go down to factory spec, probably due to having an oil cooler.

Synthetic oil - I read somewhere that it has been known to cause the rollers on roller-lifters to stay in place and not spin on some engines, which now that I think about it, may have been what I was hearing when I put synth in my ford 5.0. The lifter noise was absolutely horrendous untill I switched it back to conventional. This, along with possible gasket and seal-swell issues PLUS the money I would lose if I had to switch back to regular has me deciding against synthetic. Im not going to take the risk..

15w-40 - I actually bought 6 quarts of it and was going to go with it based on all the good things Ive read on here about it but I didnt take into account that most of you guys are up past 100k miles on your motors. I dont want to risk oil starvation or excessive oil pressures since Im at only 61k, and 50k of those miles were put on it by a little old lady! So Ill wait till much later for the Rotella. For now, Ill put it in my old, loose, and leaky ford...

Thanks for all the input fellas! Ill be sure to post the results of using the 5w-30, that is, if I notice anything.

(btw, Sub, what are the two brass fittings on the exhaust manifolds for on that 455? Are they water cooled? If so, why?)

[HUF]

Originally Posted by Sevillian273

Well Ive decided to go with some 5-30 conventional for the colder months. It will be a bit of an experiment to see if it causes any low pressure condition, which I doubt because it has low miles. I really dont like seeing such high pressures on cold mornings.... Even after It hits operating temp, The pressure still takes a while to go down to factory spec, probably due to having an oil cooler.

Synthetic oil - I read somewhere that it has been known to cause the rollers on roller-lifters to stay in place and not spin on some engines, which now that I think about it, may have been what I was hearing when I put synth in my ford 5.0. The lifter noise was absolutely horrendous untill I switched it back to conventional. This, along with possible gasket and seal-swell issues PLUS the money I would lose if I had to switch back to regular has me deciding against synthetic. Im not going to take the risk..

15w-40 - I actually bought 6 quarts of it and was going to go with it based on all the good things Ive read on here about it but I didnt take into account that most of you guys are up past 100k miles on your motors. I dont want to risk oil starvation or excessive oil pressures since Im at only 61k, and 50k of those miles were put on it by a little old lady! So Ill wait till much later for the Rotella. For now, Ill put it in my old, loose, and leaky ford...

Thanks for all the input fellas! Ill be sure to post the results of using the 5w-30, that is, if I notice anything.

(btw, Sub, what are the two brass fittings on the exhaust manifolds for on that 455? Are they water cooled? If so, why?)

By the way, little old ladies usually clog EGR tubes inside throttle body (two tubes under the blades) with carbon. You might want to check them.

[submariner409]

Yes, the exhaust manifolds are water cooled: in a marine engine environment, most often tucked under the deck or in a sound insulated box, there is essentially no airflow around the engine, so excess heat buildup must be prevented. If you look at the picture of the engine in the boat, you'll see that the manifolds are double piped into the old, unused, heater circuits in the cooling system. The larger black hoses are connected to 40' of 1 1/4" copper pipe which forms a double-pass heat exchanger under the boat, next to the keel. Exactly like a radiator is plumbed, and the entire sealed 16# cooling system uses 50/50 low-silicate green coolant. If you look harder you'll see a pair of fiberglass-lagged exhaust pipes which turn up 90 degrees and exit through the overhead canopy (dry exhaust). Thrush glasspacks. Most other installations dump raw seawater into the exhaust downstream of the manifold, which cools the gasses and pipes (wet exhaust).

[Sevillian273]

Very interesting... I guess thats why I dont see a radiator!

[logon]

I live in a cold weather area and use synthetics regularly. They lubricate well immediately upon cold weather start-up. I can buy Valvoline or Quaker State synthetics on sale for close to a dollar, so cost is not an issue. My understanding is that synthetics maintain their rated viscosity better than conventionals, and are "slipperier" than conventionals. The other thing is that oil provides about 60% of engine cooling. Since I have an HT 4100 4.5liter, anything I can do to prevent it from blowing up is a good thing.
As someone else mentioned, the best thing to do is change your oil and filter frequently. It's such a simple thing to do and the key guarantor of long engine life.

[submariner409]

logon, Good words. Some lose sight of the fact that circulating oil is the only medium that cools pistons, con rods, crankshafts, chains, valves, cams, bearings. Exactly why proper oil coolers are set up to run the oil at a temperature very close to the coolant setting under most operating conditions.

[Sevillian273]

UPDATE: So I decided to take my chances with synthetic and put in 5 quarts of Mobil 1 10w30 and a Purolator Pure One filter. So far so good! Engine runs nice and smooth with no lifter noise and oil pressure is down about 5-10 psi across the board but still within spec. I will update again if I see my pan leak getting any worse. Total cost was about $48 bucks (ouch) but I will be changing oil at 5000 now with a filter change in between.

[submariner409]

Sevillian, All around, the Mobil 1 is probably your best choice. Completely disregarding the cold oil pressure, (bypasses and pressure reliefs are open and oil is shunted all over the place) what is the idling and steady highway pressure, warm ?

A good ol' past GM engine (oil pump relief settings, really) generally runs at 10 - 25 psi warm idle, and 35 - 45 psi at around 2,000 rpm, highway.

Some engine manuals say they like 10 psi per 1,000 rpm, warm. If I saw 22 psi at cruise in my boat Olds 455 I'd be an unhappy camper.

[zentrade]

I always like to hear from anyone making the move to synthetic. I think its a good thing to do.

I think it offers great protection in very cold weather by flowing faster to the criticals,I notice my own car , which is parked outside, cranks over easier in very cold weather. This lends credibility to better flow in the cold in my opinion.

Synthetic is More resistant to heat in the summer. Less oil change intervals, less dependence on crude.

I found my car to run a little better with synthetic, I am convinced its not a placebo effect lol, It just really runs smoother.

[noahsdad]

I switched my 4100 to Amsoil synthetic three years ago, starting at 43k. The oil and filter were changed at six month intervals, roughly 4 to 5 thousand miles. At each oil change, I had a sample tested at Blackstone Laboratory. Over 5 sample periods, my engine showed a significant drop in wear metals. At best, my 4100 was wearing at a rate 62% slower than the universal average of all gasoline engines tested by Blackstone. People will argue all day about the cost/benefit/risk of synthetics, but I'm sold on the results. The proof is in the pudding as they say.

That said, I did just develop a coolant intrusion into the oil, but that had nothing to do with running synthetic. It is a 4100 after all.

[Dave S Texas]

I believe the more important thing is the oil filter. My new 4.1L engine will use 10-30w organic for the first 1000mi and then I may switch to M1. The oil will always be filtered by a Purolator Plus or Wix filter and that filter/oil will be changed religiously at 3k intervals.

[ltmax]

Lots of good discussion here, but two of the most overlooked advantages of Synthetic oil is its great increase in squeeze pressures and flash point (boiling point.)

The top piston rings in gas engines (under minimal load) operate at temperatures well above 300 degrees F. Conventional oil burns right around this temperature and this is the primary cause of the oil thickening, it's basically being slowly cooked away as it lubricates the upper cylinder walls and is thickening in the process. Synthetic oils have flash points well above this temperature, around 425-450 degrees and thus do not start to thicken or lose their viscosity in just a few thousand miles. That’s why they last so much longer, and also prove to be much more consistent in protection over their life in the engine. This is also why conventional oil can break down so quickly when your engine is under heavy loads such as towing or climbing steep hills.

The second really important benefit of synthetic oil is what's called film strength or squeeze pressure. This is how much metal to metal pressure it takes to force all the oil out from in between two pieces of metal like the crankshaft or rods and the main bearings. At engine start up (where 90% of your engine wear occurs) before normal oil pressure is reached it only takes 400psi of pressure to force out the residual film or protective layer of oil from your bearings resulting in metal to metal wear. Since synthetic oils film strength is around 3000psi, it provides nearly 8 times the protection against metal to metal contact or wear during start up or heavy engine loading especially when it's really cold and oil doesn't flow as quickly throughout your engine.

So is synthetic oil worth the additional costs? I think that if you religiously change your oil every few months or several thousand miles; live in a moderate climate; don’t routinely put heavy loads on your engine; and only want to get 150-200k out of your engine, than stick with regular oil.

If you are in the north or south where the temperatures place extra demands on your oil especially at startup; like to run your engines hard and not change the oil every few months; just want to almost eliminate engine wear; and are looking to get every possible mile of life out of your engine; you would be silly not to spend the few extra dollars for the added protection of synthetic oils. Especially when you can get 5 quarts of Valvoline synthetic at Wal Mart for less than $20.00.

[Sevillian273]

UPDATE: Ive been running my first batch of Mobil One synthetic for almost 1500 miles now. The car ran conventional for 62000 miles prior. My oil pan leak is DEFINITELY worse now having the factory cork gasket. Im about a half quart low already and theres oil all over the bottom of the cradle. But on the plus side: no lifter/roller noise and much lower oil pressure especially on cold starts.