Increasing your oil capacity will definitely increase your OCI, that is why marine, industrial, and some German cars do it. Doubling your oil capacity will come close to doubling your OCI. There are two big reasons for this 1) if you have twice as much oil it takes longer to oxidize it under normal use, and 2) the level of contaminants is almost proportional to the amount of oil in the sump. Most engine designers will agree that contaminants in your oil gradually lap/grind your engine components, causing wear. Increasing your oil capacity dilutes the contaminants, therefore decreasing wear.
Extended OCIs = Oil Capacity?
- Thread starter Buford T. Justice
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XS650,
Sump capacity has a direct impact on OCI's and that's why it's included.
The idea of multiplying by the inverse of the power density is very simple: "Power corrupts and absolute power corrupts absolutely"
In other words, if you have a muscle car and/or turbo, you are going to be doing very hard driving and NOT just loafing down the highway...
Why else would you buy the car?
Of course mpg is the alternate way of taking into account of fuel usage. But who keeps track of how much fuel they burn between oil changes? Do You???
It's much easier for the layman to determine their average fuel efficiency, which indirectly takes into account the severity of driving conditions. THAT'S why I configured the variables the way I did, to make it user friendly....
regards,
TS
Sump capacity has a direct impact on OCI's and that's why it's included.
The idea of multiplying by the inverse of the power density is very simple: "Power corrupts and absolute power corrupts absolutely"
Of course mpg is the alternate way of taking into account of fuel usage. But who keeps track of how much fuel they burn between oil changes? Do You???
It's much easier for the layman to determine their average fuel efficiency, which indirectly takes into account the severity of driving conditions. THAT'S why I configured the variables the way I did, to make it user friendly....
regards,
TS
Too slick, your equation is based on the amount of fuel consumed, even though it's buried in uneccesary calculations. The more power you use, the more fuel you consume. So hard driving in a muscle car is already considered. So there is no reason to throw in the in^3/hp. It already accounted for by fuel consumption if the driver uses the extra power.
As far a high performance cars being driven harder on average than S-boxes, that's unusual. I would go to jail if I drove my car very long as hard as a small S-box gets driven just to keep up with freeway traffic.
High performance cars typically get drivn hard in occasional short spurts unless they are on a road course.
In addition, old Lady's moderate performance cars such as an Accord or Acura put out more power per cubic inch than most muscle cars.
As far a high performance cars being driven harder on average than S-boxes, that's unusual. I would go to jail if I drove my car very long as hard as a small S-box gets driven just to keep up with freeway traffic.
High performance cars typically get drivn hard in occasional short spurts unless they are on a road course.
In addition, old Lady's moderate performance cars such as an Accord or Acura put out more power per cubic inch than most muscle cars.
Efficiency perhaps? Turbochargers increase power-specific efficiency and weight-specific horsepower with minimal added engine complexity.quote:
Originally posted by TooSlick:
If you have a... turbo, you are going to be doing very hard driving and NOT just loafing down the highway...Why else would you buy the car?
The wave of the future is likely, at least to a large extent, turbocharged engines with displacements less than 2L.
I've always run half a quart high in my car. Works out great because when I hit 3,000 miles it is exactly on the FULL mark.
Efficienn....power? Me and my friend went out last night at about midnight and just went stark raving mad in my car. Most fun.quote:
Originally posted by pitzel:
Efficiency perhaps? Turbochargers increase power-specific efficiency and weight-specific horsepower with minimal added engine complexity.quote:
Originally posted by TooSlick:
If you have a... turbo, you are going to be doing very hard driving and NOT just loafing down the highway...Why else would you buy the car?
The wave of the future is likely, at least to a large extent, turbocharged engines with displacements less than 2L.
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Anyone care to continue to play with the power density factor? I'm sure that there will be exceptions, but many engines work out to about 60hp/liter if they're normally aspirated and not variable valve timing/variable intake runner thingy.
Even a 502 crate engine follows this (seems like) mandate ..so "basically" it still comes down to a fuel number based on the sump size.
What happens when you up the hp/ltr? Does the Euro-alloy, with all the wizbang forced induction, VVT, V-intake alter the relationship in regards to sump size and specified OCI?
That is, if you plug in your Audi TT fuel economy numbers back into TS's equation with the factory spec'd (typically the 120 "C" factor) oil ...does it come out to the factory spec'd OCI with some margin for engineering:consumer fudge factor????
Even a 502 crate engine follows this (seems like) mandate ..so "basically" it still comes down to a fuel number based on the sump size.
What happens when you up the hp/ltr? Does the Euro-alloy, with all the wizbang forced induction, VVT, V-intake alter the relationship in regards to sump size and specified OCI?
That is, if you plug in your Audi TT fuel economy numbers back into TS's equation with the factory spec'd (typically the 120 "C" factor) oil ...does it come out to the factory spec'd OCI with some margin for engineering:consumer fudge factor????
I've spent a long time correlating this equation back to actual oil analysis results and it's much more accurate for high performance applications if you include the power density factor. As Gary mentions, many N/A engine now put out about 0.9-1.1, hp/cubic inch, so this last multiplier essentially has no effect on the final result. However if you have a turbo that puts out closer to 2 hp/cubic inch, I'd certainly use that knockdown factor when determining initial service intervals. For a high performance engine that's not turbocharged, the results from this equation are probably conservative....
I know it seems like you're penalizing high performance engines twice by including both fuel efficiency and power density. However these types of engines - particularly turbos - do degrade the oil faster, even if you're just cruising on the highway @ 3000 rpms. There is always a fair amount of very hot exhaust gas flowing through the turbo and there is oil flowing through the very hot turbo bearings, where it is also being sheared at the same time.
I've had to shorten the service intervals in my 1.8L, 225 Hp Audi TT by about 30%-40% over what I used to be able to run in my 1.8L and 2.0L, 90-115 Hp Jettas w/ Amsoil, and they had smaller 4.0 qt sumps, vs 5.0 quarts in the TT. Mileage with the TT is only about 10%-15% less with mostly highway driving.
TS
I know it seems like you're penalizing high performance engines twice by including both fuel efficiency and power density. However these types of engines - particularly turbos - do degrade the oil faster, even if you're just cruising on the highway @ 3000 rpms. There is always a fair amount of very hot exhaust gas flowing through the turbo and there is oil flowing through the very hot turbo bearings, where it is also being sheared at the same time.
I've had to shorten the service intervals in my 1.8L, 225 Hp Audi TT by about 30%-40% over what I used to be able to run in my 1.8L and 2.0L, 90-115 Hp Jettas w/ Amsoil, and they had smaller 4.0 qt sumps, vs 5.0 quarts in the TT. Mileage with the TT is only about 10%-15% less with mostly highway driving.
TS
Lets look at the VW Passat/Audi A4 with the small sump that's had sludge issues. These are the approx parameter to plug into the equation:
C*, 80, ie off the shelf synthetic of average quality
sump, 3.7 qts
mpg, 25
Hp, 170
cubic inches, 110
So you get:
OCI = (80)(3.7)(25)(110/170)
or an OCI of approx 4740 miles
Note that VW/Audi are recommending OCI's of 5000 miles in this engine, due to the small sump and the turbo. If you didn't include the power density, the OCI from this equation would be approx 7500 miles. That would not be advisable in this motor, given the history of this engine.
C*, 80, ie off the shelf synthetic of average quality
sump, 3.7 qts
mpg, 25
Hp, 170
cubic inches, 110
So you get:
OCI = (80)(3.7)(25)(110/170)
or an OCI of approx 4740 miles
Note that VW/Audi are recommending OCI's of 5000 miles in this engine, due to the small sump and the turbo. If you didn't include the power density, the OCI from this equation would be approx 7500 miles. That would not be advisable in this motor, given the history of this engine.
Interesting. I just ran the numbers for my 81 F-150 pickup w/300 engine. It gets 20+ mpg (I drive pretty easy, almost all highway miles).
Synthetic oil: C=80
Oil sump=5 qts
MPG = 20
Cubic inch/HP= 300/125= 2.4
Came up with 19,200 miles. I can go over 8500 on dino.
Joe
Synthetic oil: C=80
Oil sump=5 qts
MPG = 20
Cubic inch/HP= 300/125= 2.4
Came up with 19,200 miles. I can go over 8500 on dino.
Joe
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Just plug in the numbers, Brian.
What oil are you using? dino=40 GroupIII synth=80 POA=120
What size is your sump?
What's your mpg?
What is your engine size?
Multiply.
Divide by hp (it comes out the same)
What oil are you using? dino=40 GroupIII synth=80 POA=120
What size is your sump?
What's your mpg?
What is your engine size?
Multiply.
Divide by hp (it comes out the same)
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That's what I was looking for TS. This would kinda work with the 120 "C" factor for an 8 quart sump Euro with a 15k factory OCI with the semi-exclusive synth list (that's broadening all the time).
That's a very interesting point. Maybe there needs to be a fudge factor for having a turbo and a much smaller or no ding in oil life for power density.
Gary,
There is no magic to the long drains in Europe...most six cylinder German cars now have 7.5-8.5 qt sumps and most of their V-8s have 8.5-10.0 quart sumps. Combine this with fairly good fuel efficiency and you have the recipe for safely running very long service intervals.
TS
There is no magic to the long drains in Europe...most six cylinder German cars now have 7.5-8.5 qt sumps and most of their V-8s have 8.5-10.0 quart sumps. Combine this with fairly good fuel efficiency and you have the recipe for safely running very long service intervals.
TS
The 170 hp engine first became available in 2001 MY. And in that year (and thereafter), Audi recommended 10K mile OCI:
http://www.bentleypublishers.com/images//tech/audi/audi.2001.maintenance.sched.pdf
Whereas the VW recommended 5K OCI:
http://www.bentleypublishers.com/tech/vw/vw.2001.maintenance.sched.pdf
Why the difference? You had to pay for your oil changes if you had a VW. Oil changes were free if you had an Audi.
Side question:
I keep reading about these large sumps, oil capacity of 5-6-7... qts. I have a couple of Hondas, both little over 3 qts and a Mazda, again little over 3 qts, much lower capacity (all 4 cyl). Why such a big difference? Is it just a design decision or is there something in the motor design that requires lower/greater oil capacity?
thanks
I keep reading about these large sumps, oil capacity of 5-6-7... qts. I have a couple of Hondas, both little over 3 qts and a Mazda, again little over 3 qts, much lower capacity (all 4 cyl). Why such a big difference? Is it just a design decision or is there something in the motor design that requires lower/greater oil capacity?
thanks
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