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View Full Version : RPM increase with Syn oil?


KRek
11-10-2008, 11:07 AM
I know the topic of engine oil has been beat to death in this forum. However, I'd like to dis-spell a rumor. I'm in the market for a new prop for my 96 PS205. I operate at higher altitude (5000' MSL) my engine (350TBI) is operating about 100 RPM below the WOT range (4200-5000). I'm attributing this to the wrong prop setup (4-blade 13x12.5, 1:1 trans).

In an email from a 'sales engineer' from one of the prop manufacturers, a comment was made that they've seen a 100-150 rpm increase at WOT by switching to a synthetic oil in the engine and trans. I'm far from any kind of an expert on engine oil, but this doesn't seem right. If regular oil changes are made there shouldn't be any difference in the overall friction resistance of the engine and drivetrain.

Has anyone here who has switched to synthetic oil witnessed any RPM increase?

EJ OJPROP
11-10-2008, 11:23 AM
Kevin - I tried to respond to your e-mail but it was kicked back. As a disclaimer, I am not the prop guy who claimed the oil change RPM increase. I would suggest our 13 X 11 LC 1" XMP 3-blade for your application. This prop will increase your RPM more than an oil change.

TRBenj
11-10-2008, 03:35 PM
Thats an interesting sales pitch!

First of all, synthetic transmission fluid should not be used in these transmissions- its too slippery for the wet clutches and will do far more harm than good.

Second of all, 150RPM is nothing to shake a stick at- with how much hull these boats have to push through the water, it can take upwards of 25hp to get that sort of gain in performance (without switching prop sizes). I find it hard to believe that you'd see that sort of increase in power with just an oil change.

KRek
11-11-2008, 12:38 AM
Eric, thanks for tracking me down with the prop recommendation. It's very possible I fat-fingered my e-mail address on the info request page. I'll be paying a visit to my local OJ dealer come spring-time. And yes, for the record, the oil change comment came from a different mfg :)

I'm not buying the RPM increase claim by switching to syn oil. However, before completely discounting it, I was just curious if anyone here had heard that claim or has some firsthand knowledge. Synthetic is advertised to produce (slightly) better mpg in automotive applications but I've never heard of any measurable top-end power gains. I'd be interested in seeing some engine dyno data on a motor run with conventional and then synthetic oil.

TRBenj
11-11-2008, 09:55 AM
My dad has switched from conventional to synthetic (Mobil1) in his PCM Chevy (330 Excalibur). There was no noticeable change in performance.

TMCNo1
11-11-2008, 10:44 AM
Synthetic is advertised to produce................

There is the key to the whole marketing concept of many products. There is probably someone out there selling meadow muffins that they claim to taste and look like a cinnamon roll and there will be people who will purchase them just to see if they do!

93Prostar190
11-11-2008, 11:56 AM
I would not expect an RPM change due to a chageover to synth from conventional. This is more than likely a prop size issue.

On the oil front ..

On a small side note, you may notice that some auto companies with V-8 blocks, like Ford and Chevy switched their oil recommendations to lighter weight oils in the late 90's, to help with fuel mileage and other efficiencies. A lighter weight oil is easier for the parts to move through, etc, etc. Even that did not result in a change in RPM performance. Just a slightly lower resistance from the lubricant's weight. I personally did not like the 5W recommendation by Ford on my 2000 Explorer with the 5.0 liter V8 ... but they design the engines, not me.

As a part time wrenchhead, you will also not want to overfill a car's engine with too much oil for the same reasons (there are others on cars like concern for the catalytic converter) but a overfilled engine will have to work harder to move the lower parts (crankshaft, pistons, rods etc.) through the "pond" of oil in the crankcase/pan. Again, I am not sure you would see any change in RPM even with an overfilled pan.

Go with the prop theories, Eric can get you on the correct prop ... also don't discount that your Tachometer may be off a little (not likely but possible), have you checked the RPM's with another device?

Prostar Rich
11-11-2008, 04:42 PM
Eric, thanks for tracking me down with the prop recommendation. It's very possible I fat-fingered my e-mail address on the info request page. I'll be paying a visit to my local OJ dealer come spring-time. And yes, for the record, the oil change comment came from a different mfg :)

I'm not buying the RPM increase claim by switching to syn oil. However, before completely discounting it, I was just curious if anyone here had heard that claim or has some firsthand knowledge. Synthetic is advertised to produce (slightly) better mpg in automotive applications but I've never heard of any measurable top-end power gains. I'd be interested in seeing some engine dyno data on a motor run with conventional and then synthetic oil.


Here's a link to some dyno info. Fact or fiction? You can be the judge.


http://www.royalpurple.com/corvette-enthusiast.html


Prostar Rich

FrankSchwab
11-11-2008, 05:48 PM
That link shows a 3.8 horsepower increase. 1.1%.

This is in-line with the cherry-picked results reported on the royal purple website. (http://www.royalpurple.com/rp-testing-summaries.html) You know what? I'm even willing to believe that $10 / quart oil could have that much of an impact.

But, a 1.1% horsepower boost isn't worth $25 every refill for me. After all, I'd only see the improvement at full throttle operation (if I'm not at full throttle and I need more power, well, there's a simple solution to that...), and frankly I can't remember the last time I was at full throttle. And a 1.1% horsepower boost isn't going to provide a measurable boost in top speed - due to the outrageous drag a ski boat has, it would surprise me if a 1.1% horsepower boost gave better than a 0.5% top speed or RPM boost.

just my $0.02.

/frank

KRek
11-12-2008, 12:07 AM
Here's a link to some dyno info. Fact or fiction? You can be the judge.
Prostar Rich

Interesting read. The 1.1% power increase was achieved from switching from Mobil 1 to Royal Purple, both of which are synthetic. Does this mean the power increase from conventional to synthetic could be significantly more??

I'd prefer to see a test done with an engine dyno instead of a chassis dyno. Chassis dyno's are inherently quirky by design and the drivetrain on the car introduces additional variations in the data. This report also stated they installed a new K&N air filter between runs. I would hope that the filter they replaced was identical but why even replace it? Despite the author's claim they kept all variables consistent, this test was not all that scientific and the power gain they saw in the data may or may not be reliable.

Regardless, I'm still intrigued by this article. Maybe synthetic oil does provide a measurable power gain?

FrankSchwab
11-12-2008, 12:29 AM
If you follow the link I provided, you'll see a bunch of third-party (but still cherry-picked) results showing, on eyeball average, about a 3% power gain over dino oil. Possible, certainly, but changing your air filter twice as often would probably have similar impact. If it had the same impact on mileage, my 18 mpg Explorer would become a 18.5 mpg Explorer, and in 100,000 miles I'd save 150 gallons of gas, say $450 at $3 / gallon. In those same 100,000 miles, assuming I changed oil every 5000 miles, I'd spend (20*$25) = $500 more on Royal Purple than Rotella-T.

/frank

Prostar Rich
11-12-2008, 09:12 AM
Interesting read. The 1.1% power increase was achieved from switching from Mobil 1 to Royal Purple, both of which are synthetic. Does this mean the power increase from conventional to synthetic could be significantly more??

I'd prefer to see a test done with an engine dyno instead of a chassis dyno. Chassis dyno's are inherently quirky by design and the drivetrain on the car introduces additional variations in the data. This report also stated they installed a new K&N air filter between runs. I would hope that the filter they replaced was identical but why even replace it? Despite the author's claim they kept all variables consistent, this test was not all that scientific and the power gain they saw in the data may or may not be reliable.

Regardless, I'm still intrigued by this article. Maybe synthetic oil does provide a measurable power gain?




I believe the K&N filter that the article is referring to is the oil filter. I too found the article interesting.

Prostar Rich