Let the shopping begin... M809 series

I'm forming up the list of belts, fluids, , hoses, filters etc. to perform deferred maintenance on an M813.

I'm new to buying such large quantities of fluids. When buying in bulk like this, do you guys have any preferred vendors (especially engine oil)?
It would seem that strolling into the nearest Autozone for 7 gallons of 15w40 would be costly and inefficient.

Also, how many of you bother upgrading to synthetic oil on old trucks with unknown usage and an unknown maintenance record? Is it throwing money away? I'm leaning towards just using a quality, conventional oil.

We are running a special on 15W40 engine oil in 5 gallon pails

SP-2195 | 15W-40 Synthetic Blend Fleet Engine Oil 15W40 15-40
15W-40 Synthetic Blend Fleet Engine Oil for Common application for diesel trucks and other applications
NSN #:
Part #: 585862
$42.00

Thanks! Best price I've found, by far.

Walmart sells Delvac for 10.77 a gallon and delvac gives you a 7$ rebate per gallon thru the end of the year so it's only $4 a gallon.

Walmart coolant is $8 a gallon for concentrate. So 6 gallons of it and 4 gallons of distilled water is under $75.

Belts are cheaper thru ebay. The parts list for your truck is in the 5 ton stickies

You are only gonna change your oil once a year or so.

Get with member scar59 and get a spin on oil filter adapter. It makes filter changes alot easier and less mess.