excessive engine noise after changing oil to synthetic??

[locdawg]

after I changed my oil yesterday, today I started it up and drove about 30 miles (95 nissan hardbody) I used reeealy good oil and filter, but it is soo much louder now that I changed it, just wondering if this has anything to do with the cold? ( -10) or is it the oil I used which was the right kindof oil for the truck, just that I used synthetic instead..thanks..


Ian

[shortysdrop]

If you put synthetic oil in the truck when it is used to fossil fuel, you made a big mistake. You never want to switch between the two kinds of oil. Many many motors have been destroyed because of this. The synthetic oil won't perform the same and the mixture of the two (all old oil never fully drains)is never a good thing.

[nose-gobblin]

no your wrong. how else are you suposed to switch stupid. you just drain the shit out of the other oil. get a new filter and change it DO NOT GO BACK FROM SYNTECH TO REGULAR OIL IT WILL RUIN SEALS. but squeeling from where? when does it happend? like a Belt squeel? please explain

[nose-gobblin]

and oh yea, yea you can mix the oils DUH they sell a syntech mix i think castrol does it.

[shortysdrop]

Go ahead and try it yourself, put 9 years of mileage on a vehicle, then switch to synthetic. Jackass

yeah a mix would be better than straight synthetic but thats not the same as synthetic. I worked in a machine shop I know better.

[mmcleo11]

I am a mechanic, I know that changing to a synthetic after the engine bearings have been worn by mineral deposits in the regular oil will cause the Big End Bearing (where the conrods attach to the crankshaft) to wear and break. The only true way to switch types of oil is to drain the oil, fill it up with kerosene, drain the motor again, take of the engine sump to remove all traces of oil and then replace the Big End Bearings. Be careful, if your engine is making noises, it could be ready to let go already! Last time I saw this was a conrod ending up out the side of the block...

[KenOhki2112]

What are you talking about, I swiched to synth after 90,000 miles with out any problems, then swiched back to regular, then swiched back to synth, and finaly now at ~110K I'm back on semi-synth. In fact we've done that to all of our cars and it's NEVER caused a problem, 90' 240sx (110K miles), 89' prelude(130K miles), 85 toyota pick-up(>200K miles). If it causes any damage then it is extreemly little because all of those engines are in excelent shape.

[Doug Rodrigues]

As a past engine machinist, auto and then airplane engine mechanic, my personal feeling is that once an engine develops excessive wear, switching to a synthetic oil is probably a big mistake. Also, what mmcleo11 said about mineral deposits applies. I've seen high time engines very clean inside and also seen similar engines with so much gunk that the stuff had to be removed with a putty knife! Not all oils and additives are the same, in fact most manufacturers don't want you to add anything to the oil! If using STP or any other type of additive to quiet the bearings is required, then your engine is living on borrowed time. It's overdue for rebuild before the connecting rod punches a hole through the engine block! Using a synthetic oil in a high time engine is like flipping a coin: Which engine do you have?..the clean one or the gunkey one with the deposits about to melt loose because of the synthetic oil? Depending how hard one drives an engine, or how one has taken care of any particular engine, wear factor and not just the mileage is the deciding factor. Over revving a cold engine, or doing hard accelerations before warm-up cause excessive wear. * Drivers living in warmer climates don't have such a problem. In Hawaii, it's always warm. The cars (engines) there seem to go forever! The bodies will rust away long before the engines are trash.

This abuse to an engine has no bearing on mileage. Some people with high mileage engines don't have the excessive wear problem because they know how to properly operate their engines. From what I've personally seen, how one operates their engines is more important than just keeping the oil clean. Although synthetic oils have the best of lubrication qualities, they are generally thinner than mineral oils. Also, for engines that spend a lot of time in storage, systhetic oils should never be used. Unlike mineral oils, synthetic oils gravitate to the sump after a few weeks to where a "dry start" is almost guaranteed after storage. Mineral oils don't have such a problem. At each "dry start" before oil pressure develops, that's just more abuse on an engine. Many aircraft engines designed for synthetic oils use an electric pre-oiler pump OR a hydraulic pressure reservoir to get oil pressure into the system just prior to engine cranking for this very reason.

Since synthetic oils are thinner but do have the best lubricating qualities, the best time to switch from mineral to synthetic would be after engine break-in where the bearings and piston skirt clearances are still fairly tight. Use of synthetic oils at this time would then better maintain those nearly new clearances over a longer period of time. As far as not switching back to mineral oil from synthetic...anybody's guess. Airplane oil comes in mineral, semi-synthetic, and synthetic. I use mineral oil because it's cheaper and airplane engines burn more oil. May as well burn the cheaper oil. It doesn't seem to make any difference when mandatory overhaul time arrives. However, with automobiles, you can run the engine until it starts knocking...another factor to consider.

**I forgot to mention that synthetic oils were invented for jet engines, NOT piston engines. Jet engines operate at high altitudes where there was a requirement for lubricating oils that didn't thicken in the cold atmosphere. Normal operating temperatures for jets could be -40 degrees. Mineral oils would turn to molasses. Somewhere along the line, somebody decided to use synthetics in piston engines...probably a good oil salesman thought that one up.

[mmatsumotosr75]

Hows It Going?

I have a '94 Hardbody P/U 2.4L 4 Banger... Is the noise you're hearing like a gentle knocking noise? Nissan has a TSB for the ignition distributor gear clearance which causes knocking noise. Everytime I change my oil, (I use 5W-30) and it was louder when I used a synthetic oil. Anyways that fuckin' knocking sound comes back, everytime but goes away as the motor oil degrades. But maybe in your case , it's something else, i'm just shedding a little light on the subject.