I just changed the engine oil in my 05 G35 with an automatic trans with SuperTech Synthetic 5W30 with the ST7317 filter from Mobil 1 5W30 with PureOne filter. I'm not worried but something I noticed was that the RPM at 80mph is 2800 with the current ST setup while it was 3000 at with the Mobil 1 and PureOne setup. I can't really come up with a reason to why this is so...I've read in the previous posts that PureOne has more media but is NOT more restricting (as in flow rate) despite popular belief so maybe it's the different viscosities from two different companies...although they're both 5W30. I don't know, I'm hoping someone can shed some more light onto this, because I'm curious to see why this is so. I guess I should take this as a good sign? Thanks in advance.
Lower RPMs with ST than PureOne Filter
- Thread starter NissanMD
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BTW, I posted in this forum because I thought it was more of an oil issue not the filter.
My guess is you have something going on in the transmission. Oil filter is definitely not the problem. Oil should also not be the problem but maybe someone else has an idea. I have seen this with my Honda and it was the transmission fluid. Clean fluid made the torque converter overdrive work better and the rpm dropped to what is considered normal after a few flushes of the transmission fluid. Have you changed your fluid lately? Sounds like if you haven't you need to.
The car is only 8 months old and has 12,300 miles on it. I don't think it's the trans...at least I hope not.
Sounds like someone switched your gear ratios on you. Have you had it into any shops lately?
Nope, the only work done on the car has been by me, 3 oil changes.
The only time I've noticed a change in RPM at a given speed was during cold weather. The tranny would run slightly higher RPM's until the engine and tranny got warmed up. Again that was only during cold weather, and since it's anything but....got me.
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That's the only way it can happen. If the lockup converter doesn't engage. Otherwise it's a little hard to make something lose or gain in what is essentailly a straight through connection.
NissanMD, your issue has nothing to do with oil or your oil filter (or gear ratios
). Maybe your tach is/was out, or maybe your torque converter wasn't locked up when you checked it previously. Mechanically, the only thing that isn't a fixed ratio, from the pistons to the wheels, is the torque converter. And even that is fixed when the torque converter is locked. So if there's a mechanical problem causing a change in rpm, I'd look there (including the fluid). If you're cruising at a steady speed and you touch the brakes (just enough for brake lights to come on, not enough to provide a braking effect) while holding speed, the tach should show the engine speed jump a couple-hundred rpm as the TC unlocks. When you let off the brakes, the TC will lock back up and drop back to where it was running before you touched the brakes.
I assume you haven't changed to a larger tire recently!
I assume you haven't changed to a larger tire recently!
Torque converter disengagement can happen at freeway speeds when ascending grades and even in very cold weather on level terrain. The latter may happen if the fluid temperature drops below a set value. If that happens, a signal from an ATF temp sensor will result in the TCM dropping the trannie out of lockup so that the additional fluid churn will heat the fluid back up to the nominal working temperature. (That's the story in my Hyundai Sonata's shop manual, an' I'm a stickin' to it...)
I'm sorry but there is no way for an oil filter to change the RPM's.
[ August 08, 2006, 08:44 PM: Message edited by: Brett Miller ]
[ August 08, 2006, 08:44 PM: Message edited by: Brett Miller ]
It sounds like maybe could be an electrical problem (if there is a problem) because mechanically, the cars seems fine.
rpn453, the tires are still stock. However, while were on this topic, I'll be getting new tires around 15K (I know it's ridiculous). The back will be replaced with same size tires 245/40/19 but the front will be changed to 235/35/19 from 225/40/19. Will the speedometer read slower anyway because the front axle is off or will be it accurately since it's a RWD vehicle?
rpn453, the tires are still stock. However, while were on this topic, I'll be getting new tires around 15K (I know it's ridiculous). The back will be replaced with same size tires 245/40/19 but the front will be changed to 235/35/19 from 225/40/19. Will the speedometer read slower anyway because the front axle is off or will be it accurately since it's a RWD vehicle?
The speedometer reading is almost certainly determined by the rear wheel speed, so your speedometer shouldn't be affected. You could verify that by spinning the tires and seeing if the speedometer jumps up!
Ok this has never made sence to me. Why would anybody put different tires on the front and rear. Obviously they can't be rotated. So, basically, even tire wear is NOT a concern here..
Thanks rpn453 for the reply.
bighead, the car comes stock with staggered tire sizes, 225 in the front and 245 in the back. I think they do this for performance purposes and I think handling is better without having such a wide tire in the front as the back. I'm going with 235 because I can get Falkens for only 150 a tire as opposed to 250+ for tires of the original size. Also, on some cars you need to keep the staggered sizes so the vehicle stability system doesn't go into overdrive and start to act up.
bighead, the car comes stock with staggered tire sizes, 225 in the front and 245 in the back. I think they do this for performance purposes and I think handling is better without having such a wide tire in the front as the back. I'm going with 235 because I can get Falkens for only 150 a tire as opposed to 250+ for tires of the original size. Also, on some cars you need to keep the staggered sizes so the vehicle stability system doesn't go into overdrive and start to act up.
Thanks everyone for clearing it up...whoa is forum is much more active than freshalloy.com
NissanMD
Is the difference in RPM only at 80MPH?
Is the difference in RPM only at 80MPH?
No, it's all across the board but I used 80 as a reference point because it was such a even number to remember. The car is driven to about 85 on a flat plane and the RPM is taken when the speedo drops down to 80, no gas, no brake, just cruisin speed. I know this is wierd... but the RPM drop occured immediately after I changed to ST combo, I took notice of the RPM with M1 when I was driving to the hosue to change the oil. I still have a jug of M1 and few PureOnes around so I'll try that the next time and see. Maybe it is the filter...JUST KIDDING.
If it were me, I'd be so curious, I couldn't wait until the next OCI; I'd have to change it back tonight.
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