Do you really need to change the oil?, I'm just playing Devil's advocate here. Options

[VavAlephVav]

Really, aside from the cleanliness and longevity of the motor. How much of a difference does it make on the performance or power output of the motor if you have old burnt up oil that is broken down still in the motor?
Percentage wise how much power do you think you loose from having worn out motor oil that needs to be changed?

10%? 20%? more?

[Jmk91]

I put 16k on my vw and never changed oil just added and I didn't notice any difference.. I'd never.do that now but I was 16 and poor than lol. I think the biggest factor would be oil filter. I think one would brake down completely and mess things up. I know oil has oh I can't think of the word to protect your engine and keep from build up and slug. I mean running sluggy oil would play a huge roll into how it would perform but to what degree is unknown.

[Bitter]

Well eventually that worn oil breaks down, cokes and causes them to stick in the ring grooves which lowers compression and diminishes performance. Also as the gets worn it looses viscosity and begins to burn more readily which fouls spark plugs and diminishes performance. And lets not forget that excessive oil consumption forms heavy carbon deposits on the valves which can cause hot spots which can lead to pre-ignition that burns holes through pistons and can also burn the valves themselves which leads to very low compression. Oh and of course there's nothing high performance about a sludged oil pickup which causes spun bearings and connecting rods to come out of the block, which could be considered weight reduction but at that point it's not an engine but an anchor and heavy anchors perform the best so...

Just change your damn oil on time. 3K, 5K, 7K, 10K, whatever interval works for you given the type of driving, engine condition, and quality of oil and filter used.

[VavAlephVav]

Well eventually that worn oil breaks down, cokes and causes them to stick in the ring grooves which lowers compression and diminishes performance. Also as the gets worn it looses viscosity and begins to burn more readily which fouls spark plugs and diminishes performance. And lets not forget that excessive oil consumption forms heavy carbon deposits on the valves which can cause hot spots which can lead to pre-ignition that burns holes through pistons and can also burn the valves themselves which leads to very low compression. Oh and of course there's nothing high performance about a sludged oil pickup which causes spun bearings and connecting rods to come out of the block, which could be considered weight reduction but at that point it's not an engine but an anchor and heavy anchors perform the best so...

Just change your damn oil on time. 3K, 5K, 7K, 10K, whatever interval works for you given the type of driving, engine condition, and quality of oil and filter used.

...Thank you.


Some of you may remember that I've told you I am working on my degree in Mechanical Engineering, and I am a bit older than your typical student. I've also got a number of years of hands on experience in other technical fields like electrical and refrigeration, but have no formal training in automotive though I've learned as much as I can from books just so that I can survive (because unless you live in a big city you Must have a car, or you don't have a job).
And I am involved in this thing they call the SAE Baja racing team. They give us a 10hp B&S and we have to design and build the rest of the single seat dune buggy from scratch, then we compete against all the other engineering schools in the country, even international.(the Canadian teams are no punk.)
See here http://bajasaemaryland.umbc.edu/

This is my first semester on the team and so I'm just trying to learn about how the events run and gather all the info I can, the Seniors are the ones running the show. I've tried to offer some advise without stepping on anybodies toes or acting like "Hey you ****ing stupid kids don't know what you're doing."
These guys say the motor they had last year Sucked, don't even know what's wrong with it, Briggs & Stratton just sent us a "bad one". So they replaced it this year and they still swear up and down that it's only making 8hp instead of 10.
Well, I opened the oil fill and dipped my finger in, what I pulled out was dark, soot-like, muddy on one part and clear watery on the top, and when I rubbed my fingers together I could feel metal in it.
So, I suggested that we should change the oil. I figured that could be one of those little things I could take care of for them so they could be busy with the other important stuff they need to do.
Instead, They all yelled at me as if that was the STUPIDEST thing they have ever heard. And that really hurt
I really have a bunch of kids, who've never had a real job, and don't even work on their own cars, getting in my face and telling me to shut the **** up.
the next time that happens somebody is going to be wearing a big red hand print across their face for the next week.

Lucky I only have to put up with these kids for another couple of weeks then they graduate and go away. The guy who's going to be in charge next season is in his 30's and spent most of his youth hanging out at the drag strip day and night, so I feel real good about next season.

I just wanted to share because I figured you guys would think this's real funny. One of these little ****-heads just got a job as a design engineer for Peterbilt too. (lol)

[Bitter]

If the oil is that bad then it could be contributing to the cylinders (well single here) washing down and not holding compression. People forget that oil coating the cylinder wall lubes the rings AND helps them to seal. A cylinder washed down with gasoline will have a substantially lower compression reading than one lubed with oil. Heck, look at wet vs dry compression test scores! Not only that but if that engine has a crank case breather that vents to the intake than the volatiles in the oil will gas out as the engine heats up and be creating a much richer mixture. I assume it's one of the new fangled EPA/CARB cert engines with a non adjustable carb? Those can be real touchy about old gasoline and dirty jets. No needles to adjust to get the best power which sucks, they always smell a little lean to me but that wouldn't jive with NOx targets, more likely they only meet emissions when they're new and clean, little dirt and they go lean. Run some gas with Seafoam (strong mixture) through it (maybe 1/4 tank gas and make it a 8:1 ratio gas-Seafoam) and see if she perks up any. Of course change the oil too and check compression, the cylinder could be damaged by poor lubrication and glazed up now. Wet and dry compression should be fairly close, within 20psi I think. It's been a while since I did any real work on lil engines. I shaved a head and cut some valve reliefs in a mower engine once, that was fun. Needed 89 octane or better not not diesel after that, but boy did it make easy work of thick wet grass! Little 2 strokes are much more fun to me, the smell great when they're tuned just right. Had a friend with a moped with a Minarelli engine on it, swapped it's cylinder from 50cc to 75cc and bumped compression from 8:1 to 14:1 with a Bosch Supercoil to jump a .045 gap instead of the stock .025 gap. Just the bigger spark made as much difference as the bump in CC and CR did! But that's cause the oil in 2 stroke mix is a real damper on combustion, but the extra compression really helps. 2 strokes are funny though, the more oil you add the leaner it runs so you can tune it and then tune it again!

[Box]

Generally the rule of thumb is 5K for conventionals, and 10K for synthetics with some claiming 15K. This would be under normal conditions that the majority of drivers experience. An oil cooled turbocharged motor burns up the oil sooner for the obvious reasons, and a truck that spends most of the time towing fall more towards severe conditions and really need changed more often. One thing to note is when using synthetics make sure to grab an oil filter that's meant to last for the extended duration between oil changes. The thing to do would be do an oil change and then drive the car for about 5,000 miles and send off a sample to Blackstone Labs or the like and they'll say exactly when you should be changing your oil. If you live in a warm climate and do all of your driving at 55 mph obviously your oil will last much longer than someone that lives in an ice box that does nothing but city driving.

This post has been edited by Box: May 14, 2015 - 11:42 PM

[PegGTS]

University of Manitoba SAE for the win! We don't mess around!

[Bitter]

Oh my yes, take some of that oil out and send it off to Blackstone and shove the report in their faces with a big huge grin.

[SwissFerdi]

2k for the Miata and 3k for the Celica, 10W-30 and 5W-30.

This post has been edited by SwissFerdi: May 15, 2015 - 11:39 AM

[Bitter]

University of Manitoba SAE for the win! We don't mess around!

It runs on tar sands and maple syrup right?

[PegGTS]

University of Manitoba SAE for the win! We don't mess around!

It runs on tar sands and maple syrup right?

You bet it does!

[Bitter]

Do you apologize when you lap someone? ok, done with the canada jokes.

[Box]

2k for the Miata and 3k for the Celica, 10W-30 and 5W-30.

Remind me to upsell you on air filters every 5K.