My first-time to perform an oil change

[bramc]

My new-to-me bone-stock well-maintained 1985 Limited wagon with 130k+ will be here next week (it’s snowed in). It’s been years since I have performed my own oil change, and certainly my first on an American Motors “classic.” But I really want to get in there and familiarize myself with the engine whether an oil change is necessary or not. I have some very basic questions about how to go about it:

Recommended oil? I live in Georgia so I’d love advice on what weight. Synthetic or conventional? It seems to me that in the early days of Mobil 1 some people were worried about switching to synthetic in an older car.

Installing the filter: I’ll definitely use a high-quality (likely Wix) filter but I have no idea how tight it should be twisted on. Stupid question I know. Also, there seem to be different sizes out there that claim to fit the vehicle.

Drain plug: should I go ahead and buy a new one. Does it use a crush washer and should that be replaced at the same time? And again, how tight?

Thanks for reading.

[amarshall]

Welcome to the forum.  When you get a chance, post some pics of your Eagle!

I’m also in Georgia, are you close to Atlanta?

I’ve always gone with a high quality conventional oil like Penzoil or similar.  From memory I used 10w-30 and I can confirm that a WIX 51626 is the one you want.  Get it as tight as you can by hand, then give it about a half turn with a filter wrench and you’re done.  Don’t forget to spread a little oil on the rubber gasket before you sprint the filter on.

I don’t think the oil pan drain plug uses crush washers, no need to buy a new drain plug unless something is visibly wrong with yours.  My manual says the torque spec on the drain plug is 30 ft-lbs, if you have a torque wrench available.  If not, I’d go “firmly tightened, but no need to wallop the thing”.

If you have not yet picked up a factory service manual, hop onto one of the auction sites and grab one.  They are a very valuable reference for anything you need to do.  Also, RockAuto is a good source for parts - they have most of what you’ll need and the prices are very low.

Good luck with your new classic!

[bramc]

Thank you. That's exactly the straightforward response i was hoping for. I'm in Marietta, BTW.

[Canoe]

I'm of the opinion that it's not quite so straight forward.

First
I'm a fan of synthetic over conventional oil, for three reasons.

• When turned off, more oil stays up on the lubricated parts, reducing wear on start-up. 
• Less resistance when turning over to start.
• It resists heat breakdown more. (This doesn't mean you could/should risk your engine by extending the time between oil/filter changes, as it still gets dirty & contaminated by combustion by-products.)

Second
Since the 258 engine was designed, while each iteration of oil standards has improved oil quality over time, some lubrication additives were reduced or removed for emissions reasons. That removal is said to matter for wear on our engine's flat tappet cams. Some think this doesn't matter. I think it does. (In particular it very much matters for some upgrades to my engine.) YRMV

To get the original lubrication protection (not performance) designed for, when using a modern spec oil this requires that you:

• add an appropriate lubrication additive, typically a zinc additive (ZDDP), with every oil change, or
• buy a modern oil formulated for older cars that has appropriate additives already in it.

Both can be expensive options.

After a lot of information chasing, I've gone for a somewhat cheaper option: using Shell Rotella T6 Full Synthetic, an oil that was formulated for both diesel engine (specifically valve requirements) and gasoline powered engines. The additives for diesel valve protection are good for our cams.
(I've also gone for a wide range grade that matches the wide range of temperatures I drive in.)

Do check the min/max temperatures where you drive (https://en.wikipedia.org/wiki/Marietta,_Georgia), against what the Eagle manual says to use. Slightly different tables for that recommendation, depending on which Owner/Driver Manual, RM or TSM.
For http://amceaglesden.com/guide/B_Maintenance, given the January average low is 30 F, that puts you into 10W-30 or 10W-40; given what the high temperatures can be where you are, I'd be going with the 10W-40.
However, given the record low below 0 F for three months, perhaps the 5W-30 in the table makes sense. And again with those highs, I believe you should consider a 5W-40 that wasn't available back when that table was made.
The Rotella T6 Full Synthetic is available in a 5W-40, if you want an oil that already has more of what's required for our flat tappet cams.

Here's the full version
https://forums.amceaglesden.com/index.php?topic=47179.msg363983#msg363983

[bramc]

Thank you for all of that. I went to pick up oil at NAPA and they really, REALLY didn't want me to put synthetic into an older car. Your points are strong and I'm inclined to go Synthetic.

[Canoe]

... they really, REALLY didn't want me to put synthetic into an older car. ...

lol
They live on truisms. You'd blow their minds if you went over the formulation technical specification reasons for using Shell Rotella T6 Synthetic 5W-40 "Diesel oil" to meet the needs of your older flat-tappet gas engine. In my NAPA, the two young guys were standing there with their mouths hanging open (one knew what flat tappet was), while the older guy has nodding along and then said that's right, and also for oil shear, then went into details which went over my head.

Using 10W-30, I went synthetic in my Eagles back in the 90's. Engine turns over significantly easier. Yours may already be on synthetic.

Do note from the thread I linked to

[...]AMC doesn't get much love, but Jeeps, even early Jeeps do.

Without going to one of the premium & expensive high ZDDP oils formulated for older (flat tappet) engines, the toss up for a 4.2/4.0 era Jeep flat tappet in an SN rated oil seemed to be between Mobil 1 or Castrol Edge. I'd have liked Castrol Edge Extended Performance (better additives which last longer), but it isn't available in the xW-yy grade I wanted. (And over SN, I'd like the latest SP rated oil too, but it's too new to have wide choices yet.) Castrol Edge is thought to likely be slightly better than Mobil 1 for Jeep engines, due to a better match of its additives to the needs of that era of engine. Both would still require some user added additive for flat tappet. [...]

The step beyond Mobile 1 Synthetic or Castrol Edge Synthetic, is the Shell Rotella T6 Full Synthetic.

From the temperatures covered by the different grades, the temps listed for your area, and the Eagle oil chart, I'd be strongly looking at 10W-40, or even 5W-40.

The problem is, I'm on the fence between 10W-40 and 5W-40 for your record lows. BUT, for engine longevity I want oil flowing and flowing well for all my starting. For that when-cold flow, hence longevity, I'd have to give the nod to 5W-40.

Here's why I'm on the fence.

Looking at the chart (in other thread) of modern temperature ranges listed for modern oils, a modern 10W shows as covering to -30 C, which does cover your record lows. But again, longevity.

To look at the type of data they derive the temp/grade chart from, from the W oil viscosity graph (in other thread),
* at your average winter low around 0 C the difference between 10W and 5W is negligible.
* at your record lows, the difference between 5W and 10W is meaningful, but while 10W is thicker than 5W, 10W is NOT horribly thick at those temps. 10W should be fine, but again, longevity.

IMHO, I believe the bottom line is: a 10W-40 would be fine, a 5W-40 would be better for when-cold flow, hence longevity. If you travel in winter to colder regions (further north? higher altitude?), then I'd be stronger on the 5W-40.