Oil Change Interval

[Pat]

On Yahoo yesterday Consumer Reports.Org reviews oil change intervals and finds that many service outlets recommend three thousand mile intervals between oil changes. CR claims this is a myth and that a car owner should change oil as per manufacturer's recommendation. Which in our case is five thousand miles (5K) for normal driving.

I noted that differentiation when I bought my MM and a year later my GM. The answers from the dealer where either out right lies (the service manual says so, it doesn't or because the chemical properties of additives in the oil break down (?).

I'm looking at the oil when I change it and other than being significantly darker than new there doesn't seem to be any thickening or foreign matter in the old oil.

I would save about 40% of oil change cost by going to 5K interval.

For me that would be $90.00 per year for one car or $180.00 per year for both cars at dealer prices. We have about the same mileage on both the GM and MM.

If I change the oil myself and I'm doing that now with my new tool, I'll save $108.00 per year. Well, that puts into a better perspective.

Is there a downside?

[bob6364]

Yes!....The oil company exec's would all have to buy the medium hot tub instead of the large one for their new mansions.....

[FordNut]

I've always used the 5k interval.

[Bluerauder]

Yes!....The oil company exec's would all have to buy the medium hot tub instead of the large one for their new mansions.....
Bingo ......

And they would have to settle for the 48 foot boat instead of the 60 footer. :D

[Marauderjack]

I've always used the 5k interval.

^^^+1^^^ VERY easy to keep up with at 5K intervals!!!:beer:

[JimmyXR7]

On Yahoo yesterday Consumer Reports.Org reviews oil change intervals and finds that many service outlets recommend three thousand mile intervals between oil changes. CR claims this is a myth and that a car owner should change oil as per manufacturer's recommendation. Which in our case is five thousand miles (5K) for normal driving.

I noted that differentiation when I bought my MM and a year later my GM. The answers from the dealer where either out right lies (the service manual says so, it doesn't or because the chemical properties of additives in the oil break down (?).

I'm looking at the oil when I change it and other than being significantly darker than new there doesn't seem to be any thickening or foreign matter in the old oil.

I would save about 40% of oil change cost by going to 5K interval.

For me that would be $90.00 per year for one car or $180.00 per year for both cars at dealer prices. We have about the same mileage on both the GM and MM.

If I change the oil myself and I'm doing that now with my new tool, I'll save $108.00 per year. Well, that puts into a better perspective.

Is there a downside?

Convential oil comes out of the refractory process as 20 wt or 30 wt and the oil companies use additives to make the oil 5-20W or 5-30W. After a while, the synthetic additives break down and the viscosity decreases. The oil thins, not thickens with use.

The full synthetic oils do not use the base oil resulting in less percentage viscosity loss and more original additives.

If you use the full synthetic oil, the oil can last over 5,000 miles. If you use the conventional oil, the oil should be changed after 3,000 miles.
The other reason to change the oil, is if the oil should loose its honey color. Some people wait until the oil is black, but that is too late and there is increased risk of wear damage to the engine.

If you are drag racing or hot rodding, use fresh synthetic oil.

Jim

[Phrog_gunner]

The service manual actually DOES say so. It recommends 3k oil changes for cars that see harder service. So instead of questioning you on how you drive and how long your car idles and what speed you drive and how much the car sees WOT, they err on the side of caution (and their bottom line) and just refer to that as a default.

[ImpalaSlayer]

5k here, and she is due for a changin!

[fastblackmerc]

Every 5k on all my cars. Best thing to do is get the oil analyzed by a lab. I use Balckstone Labs. They recommended a 6k oil change but that's too hard to remember. They send you the sampling kits free and I think they charge $20.00 a test.

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

[Glockafella]

Every 5k on all my cars. Best thing to do is get the oil analyzed by a lab. I use Balckstone Labs. They recommended a 6k oil change but that's too hard to remember. They send you the sampling kits free and I think they charge $20.00 a test.

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


Nice info!

I change mine every 3K with synthetic...I cant stand any dark or black in the oil...it starts becoming less translucent after 2K miles and when it gets to 3K its dark and so I change it. My personal preference only. The dealership I get it changed at ALWAYS remind me it isnt nessisary until 5K...but I do it if I have the $. Cant hurt.

[Glockafella]

Just ordered my free analyzation kit, cost 22.50 for them to analyze.

[blackhueys]

lets see now oil change cost is what about 40 if ya do it yourself maybe a bit more at the dealer like about 50 to 80 not sure just guessing there. now compare that to the cost of a new engine? I think I will over change my oil i can do a lot of oil changes for the cost of a new engine better safe then sorry is my idea. just my 2 cents now to each there own.

[RF Overlord]

the oil companies use additives to make the oil 5-20W or 5-30W. After a while, the synthetic additives break down and the viscosity decreases. The oil thins, not thickens with use.That is true with wide-range conventional (mineral) oils like 10W-40. To make an oil have that range, blenders add VIIs (Viscosity Index Improvers). It's these long-chain polymer VIIs that shear with prolonged use causing the oil to lose viscosity. 5W-20 and -30 oil have less of these VIIs. With even more prolonged use, conventional oil will begin to oxidise, causing it to thicken. Synthetic oils have little or no VII and are far more resistant to oxidation.
If you use the conventional oil, the oil should be changed after 3,000 miles.That may have been good advice 30 years ago when engines were less efficient and produced more blow-by and fuel dilution, and oils were Group I and of poor quality, but today's engines are far cleaner and oils are superior Group II and Group II+ so that 5,000 miles is now the norm. Synthetic blend and full synthetic Group III and Group IV oils can go much farther while providing the same protection.
The other reason to change the oil, is if the oil should loose its honey color.That's another myth. It's very difficult to judge visually whether an oil has darkened because it's doing its JOB and holding contaminants in suspension, or whether it has oxidised or become excessively contaminated and is beyond its useful live. The only true way to tell an oil's condition is to have it analysed, as others have mentioned.

blackhueys, changing the oil more often than necessary is false economy as it does not result in any significant improvement in engine wear. In fact, SWRI (Southwest Research Institute), who does all the oil testing for the major manufacturers, has released studies showing that changing the oil more often than every 3,000 miles actually INCREASES wear.

Pat, save your money and your knuckles and go to a 5,000-mile OCI. There is no downside.

[Glockafella]

Just dont wait 60K miles

http://www.mercurymarauder.net/forums/showthread.php?t=58462&highlight=sludge

[Pat]

Thanks fellas, good info about viscosity. I'll digest this and modify my oil change schedule.

Prolly to 4, analyze and then adjust.

Regards

[Phrog_gunner]

Even the producers like BMW and Mercedes recommend ~5,000 mile intervals, no one disputes their engineering.

[Canadasvt]

Even the producers like BMW and Mercedes recommend ~5,000 mile intervals, no one disputes their engineering.
My bud's BMW MINI Cooper S didn't need it's first oil change until 16,000km?

[scruff]

i use amsoil 5w20 full synth and i change the oil every 10,000km

[Big Black Beast]

I use the motorcraft synth blend every 5,000 miles. Very easy to know when it needs to be done. I can't keep track of it every 3,000. I'm not organized enough to write it down.

[Glockafella]

In fact, SWRI (Southwest Research Institute), who does all the oil testing for the major manufacturers, has released studies showing that changing the oil more often than every 3,000 miles actually INCREASES wear.




Really? any documentation to back this up?

[frdwrnch]

This is one of the most frequent questions I am asked. For my customers I try to align my recomendations with the owner's manual recomendations. Typically for my customers I recomend a 5000 mile service interval. In our immediate area most of my customers qualify for severe service intervals. Our Motorcraft oil is a semi-synthetic so it offers more protection than the organic or mineral based oils.
Personally, I think it's cheap insurance. We have a '97 Crown Vic w/168k miles on it. This car will use 1qt of oil in 3000 miles. If I do not change it and I choose to add a quart. It will use a quart every one thousand miles thereafter until I change it.
If you have a car with over 75000 miles on it the frequent service interval may allow you to spot a minor problem before it becomes a major problem.
I can not agree with the position that used oil decreases wear more than new oil. I just installed a professionally built stroker crate engine (Phoenix engines) in a vintage Mustang and the break in directions are very explicit requiring motor oil additive and two oil changes within the first one hour of operation (one after initial run in and camshaft break in, another after 30 minutes run time).
One thing is certain. Overhead cam engines are inherently more sensitive to oil quality. Our engines do not have replacable cam bearings and the cams are riding on a layer of oil between the head casting and the camshafts themselves. A few pieces of grit and the clearance is compromised. The repair: a reman cylider head(if you're lucky).
I'm keepin' it Old School! I'd rather spend a few more bucks on changing my oil and looking for future issues than skimping and having a surprise overheat condition because I didn't notice that leaking water pump. Just my .02.

[MiltownCvLx]

Seeing documentation would be nice to see cuz ive always done oil changes every 3k

[Glockafella]

I agree that 5K+ mile oil changes is okay to save $, but I didnt know I was causing harm to my motor by changing every 3K.

I would say my driving is severe, I live in Missouri, so I drive in everything from 110 degrees to -20 degrees. I drive short distances(5 miles or less 90% of the time), and I like to push my car once in awhile.

I check my oil every month for level and color quality.

I hope I am not doing myself in.

[RF Overlord]

Glockafella, I didn't mean to imply that a 3,000-mile OCI would cause harm to your engine, only that changing the oil more often than necessary is not the "cheap insurance" many people like to think it is as it doesn't IMPROVE anything. Most engine wear occurs in the first 3,000 miles after an oil change and steadily declines after that.

Here are 2 links in support of my statement:

SWRI study (http://www.swri.org/3pubs/IRD1999/03912699.htm) Read the last paragraph.

BITOG thread (http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1053159) Read the reply from GMFan, which is from the Paradise Garage oil study.

[SC Cheesehead]

Glockafella, I didn't mean to imply that a 3,000-mile OCI would cause harm to your engine, only that changing the oil more often than necessary is not the "cheap insurance" many people like to think it is as it doesn't IMPROVE anything. Most engine wear occurs in the first 3,000 miles after an oil change and steadily declines after that.

Here are 2 links in support of my statement:

SWRI study (http://www.swri.org/3pubs/IRD1999/03912699.htm) Read the last paragraph.

BITOG thread (http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1053159) Read the reply from GMFan, which is from the Paradise Garage oil study.

Bob, absolutely correct. One of the best practices of reliability-centered maintenance (from a performance perspective as well as cost) relates to condition-based vs. interval/time-based maintenance schedules. Thus, the best way to determine oil change frequency is by oil analysis versus a set mileage or time schedule.

[252life]

Even the producers like BMW and Mercedes recommend ~5,000 mile intervals, no one disputes their engineering.


In Europe pretty much all cars have flexible intervals depending on your driving style / fuel consumption. On older cars it's every 1500 liters of fuel used, on newer cars it's every 2500 liters of fuel used.

For most cars that works out to about 20000-30000km or 1/year. (30000km = 18641miles)

European manufacturers have tried to increase the intervals in USA, but it's very difficult. It's mostly due to old habits that are difficult to overcome, and the oil company's have no interest in changing that and seeing the sales drop.

[rickey1987]

I use amsoil in my car. I can go 35,000 miles or a year. I've had the oil analyzed and before I started using it I had my friend who turned me on to amsoil analyze his oil and show me the results as well. My car runs a bit cooler as well and I use it in my bike and it runs cooler. Call me crazy for going that long without an oil change but I've had it analyzed and its all good.

[SC Cheesehead]

I use amsoil in my car. I can go 35,000 miles or a year. I've had the oil analyzed and before I started using it I had my friend who turned me on to amsoil analyze his oil and show me the results as well. My car runs a bit cooler as well and I use it in my bike and it runs cooler. Call me crazy for going that long without an oil change but I've had it analyzed and its all good.

My point exactly! If analysis indicates that your oil is still performing, why spend money to change it out?

[vkirkend]

Convential oil comes out of the refractory process as 20 wt or 30 wt and the oil companies use additives to make the oil 5-20W or 5-30W. After a while, the synthetic additives break down and the viscosity decreases. The oil thins, not thickens with use.

The full synthetic oils do not use the base oil resulting in less percentage viscosity loss and more original additives.

If you use the full synthetic oil, the oil can last over 5,000 miles. If you use the conventional oil, the oil should be changed after 3,000 miles.
The other reason to change the oil, is if the oil should loose its honey color. Some people wait until the oil is black, but that is too late and there is increased risk of wear damage to the engine.

If you are drag racing or hot rodding, use fresh synthetic oil.

Jim

I respectfully disagree. The only way to truly know what your oil change interval shoulod be is by doing a oil analysis. I do this regularly for my MM and SRT-10. The intervak for the MM is 5500 - 6000 miles using dino oil and the SRT-10 is 3000 miles using synthetic. You have to do an analysis to be certain.

[RF Overlord]

European manufacturers have tried to increase the intervals in USA, but it's very difficult. It's mostly due to old habits that are difficult to overcome, and the oil company's have no interest in changing that and seeing the sales drop.Bingo.

The oil companies and the quick-lube industry are the only ones who truly benefit from 3,000-mile OCIs. I read on BITOG about a document from JiffyLube a few years ago stating that if everyone who changed their oil at 3,000 miles went to 4,000 miles they would not be able to sustain their business model. I actually had one JL "technician" tell me that my company was risking expensive engine damage because it specifies a 5,000-mile OCI for vehicles in my department. I politely thanked him for his concern. :shake: