Greetings folks. I have an 08 G35 with about 105k miles on it. Seems to be running well. I have always had my oil changed at the scheduled interval of 3750 but it got me wondering when I see and hear about all kinds of cars not needing changes until every 8-10k miles. I figured if I get the nice Mobil 1 full synthetic, I should be able to get a solid 10k miles out of each change.

Does the board think this is a good idea to use good oil and stretch the interval or stick with the guide's every 3750?

 

Long story short with my personal opinion.

Stick with conventional oil. The engineers designed bearing clearances / oil takeup around a specific viscocity and type of oil. On a low mile engine the lower friction coefficient from synthetic outweighs the lack of takeup on bearings. On a higher mile engine it's roughly the same on either side of the equation, lower coefficient = bearing takeup due to larger clearances however the additional wear on the rings increases the chances of oil consumption directly into the combustion chamber which negatively affects performance and the longevity of your plugs.

Go ahead and try out a run of synthetic oil but if you experience ANY noticeable oil consumption across the 3k mile mark (meaning it drops more than 1/8'th of the dipstick hash length) then switch back to conventional. If you want actual scientific comparison then get an engine oil analysis BEFORE and AFTER switching to synthetic and compare the results, Blackstone EOA isn't that expensive and you will have actual comparison results instead of a bunch of internet opinions.

EDIT: The only true way to measure when the proper time to change your oil is to get an EOA, if you decide to go synthetic then you will have a baseline from conventional and synthetic, try pushing your oil change out to 7k, 10k, etc and compare the EOA numbers. You can google what the various metals in the report would mean for engine wear but if anything is out of the norm they usually just write in the comments section what the problem could be.

https://www.blackstone-labs.com/

DOUBLE EDIT: A quality oil filter is more important than the oil you are using. I like K&N, do your own research into what would work best for your specific application.

Everyone has their own opinion on the subject and it's usually a HOTLY debated item so prepare for walls of advice, counter-advice, name-calling, dick-measuring rhetoric, and usually a meme or two.

 

I had an analysis done at Blackstone on my 105k mile '07. They recommended 5k mile intervals. I tend to stick to about that. I've also found that a 50/50 mix of conventional and synthetic 5w30 seems to keep it quieter, though in hot weather, it does still get a bit of a tic (like most every other one of these cars that I've been around). There was some thread on Bob is the Oil Guy about the 50/50 thing and VQ35HRs.

It's also never burned any significant oil, be it 100% synthetic or conventional. That is a bit of an old wives' tale.

 

If you use conventional oil, stick with around what Nissan/Infiniti recommends (3750 miles (short trips, stop/go driving, etc) or 7500 miles if it's primarily highway driving). If you use synthetic, you can obviously go longer (hard to say how long with doing some analysis). Also, it's a waste of money (it's yours though, so do what you want !) to use synthetic and change it at conventional oil intervals.

Regarding what oil to use, Nissan/Infiniti only recommends that it meet API "SM" spec and is 5W-30. They do not recommend conventional nor do they say not to use synthetic. If the synthetic you choose meets those, it will be fine.

 

Found an oil analysis on an '07 G35X where the person uses a well-known synthetic - and 0w-40 at that. Previous oil change was ~9k miles and the recent one was ~10.5k miles, then the analysis was done. Based on the results, Blackstone recommended 12k for the next interval ! Of course, that coincides with what the oil manufacturers say their oils can do.

I do realize this is just one sample too....

 

Huh. My sample was on Pennzoil Platinum 5w30 synthetic. I took a sample at around 900 miles on the oil, and asked how long, time-wise, it's OK to leave oil in the car. Here's what they said:

In modern engines like this it doesn't really matter if the oil stays in place a year or two. The block is sealed up tight enough that corrosion isn't a problem. This oil only has 900 miles on it so far and that's why wear is so low. Our averages show typical wear from this type of engine after about 4,900 miles on the oil. You haven't changed this oil yet (good!) and it should be fine to run it 5,000 miles total. No contamination from fuel or water was present. Air and oil filtration are great. Nice!

 

At 900 miles, they don't have sufficient wear data to determine how long to run, so it looks like they go safe and say 5000 miles. Send in a sample from when you drain it and change it around 5000 miles and see what they say.

 

Thanks for the responses guys. I am really not mechanically inclined so I will do a bit of googling based on the responses and of course, re-read them all. I generally am making short trips, about 20 minutes each way to work with a little bit of stop and go. Occasionally I make an hour long drive here and there on the interstate. Sounds to me like a synthetic blend oil (not the primo stuff, but middle grade I suppose) would be the best option and keep it around 5000 miles.

 

You can buy full synthetic oil in 5-quart bottles for around $20 every day at Walmart and Fram's top-end filter (XG6607) for $9. No need to go "primo", especially if you're changing it at 5000 miles. Don't worry about it.... It will be fine.

 

Nice. I don't change my oil any longer. I suppose it would then be safe enough to just go to Walmart and have them do the change. Just select the Mobil 1 synthetic and a good filter and let them do it? I've never brought my own oil to a shop to get it changed.

 

I'm not sure if Walmart will allow you to supply the oil and filter although it might help if you buy it from there. All you can do is ask. Most will steer people away from oil-change options like Walmart, quick-change places (Jiffy Lube, etc), and so on. I see posts/comments from people who do have a shop that lets them supply the oil and filter but they're usually independant places or it belongs to a "friend". Saw one person say they get charged $15 for an oil change when they supply the material - it hardly seems worth the shop's time and effort to do it for $15 though.

 

Good points. The place I will likely bring it to does a Mobil 1, tire rotation for about $70. If i can get 5000 miles out of that, i think its a fair price.

 

To be honest, that's a pretty steep price (to me) but if YOU consider it fair, that's all that matters. Mobil 1 oil is pretty normal stuff nowadays.

The Walmarts around here are using Castrol as their normal fill and for $40 you can get a synthetic blend oil change. Not sure what filter they use though. Worst case, you buy a Fram XG6607 and tell them to use it instead of the one they use and call it even. Tire rotation is a couple of dollars per tire.

Even the local Infiniti dealer will do an oil change for $40 using a synthetic blend and a Nissan filter. Tire rotation will be extra though.

Do you have Discount Tire stores around you ? They do free tire rotations for anyone. They don't advertise this but it's true. They do promote it as part of the service they offer if you buy your tires from them but even when you don't, they'll still do the rotation (in hopes you will buy from them in the future).

 

I actually do have a Discount Tire about 5 minutes from me. To be honest, I don't mind buying my oil and filter from Walmart and having them do the change. I just got 4 new tires on my car and the place I bought from does the free rotation for life of vehicle. So i could technically just do that.

 

I personally wouldn't let a "quick change" shop lay a finger on my car. As simple as an oil change is there's some important details that can be skipped. They are the types of places to reuse a crush washer, leave the drain plug loose, filter loose, not change the filter and other things. My brother went to a jiffy lube with his altima and paid for a oil and filter change. I looked under the car and he still had a nissan filter, which I highly doubt they stock. These are just the type of people who work at these places. If they knew they were worth more as an employee, they wouldn't be working at walmart or jiffylube. Get a fumoto drain valve installed and diy. You'll be under your car for less than 60 seconds