Buick 225 Dauntless takes 5 quarts with filter; AMC 258 takes 6 quarts with filter. Both are flat-tappet engines and need a modern oil with adequate zinc (ZDDP) — Rotella T4 15W-40 or Valvoline VR1 are the safe defaults.
The CJ-5 ran three very different engines across its production: the Hurricane F4 four (1955–1971), the Buick 225 Dauntless V6 (1965–1971), the AMC 232 inline-six (1972), and the AMC 258 inline-six (1972–1983), plus an AMC 304 V8 in some years. Oil-change procedure is identical across all of them. Capacities are the part that catches people out.
The Buick 225 takes five quarts of oil with a filter change — that's straight from the factory Jeepster service manual. The AMC 258 is closer to six quarts with the filter installed, though sources vary slightly. Some forums say "five plus one for the filter," others measure six. Trust the dipstick after the change, not the spec sheet — different aftermarket filters hold different amounts of oil and you can be a half-quart off either way without realizing it.
Oil weight: both engines are flat-tappet designs (no roller lifters), which means they need a modern oil with adequate zinc and phosphorus (ZDDP) to prevent camshaft and lifter wear. Most off-the-shelf passenger-car oils since 2007 have reduced ZDDP to protect catalytic converters — fine for modern engines, bad for an AMC 258. Use Rotella T4 15W-40 (diesel oil, high ZDDP), Valvoline VR1 Racing 10W-30 or 20W-50, or a dedicated classic-car oil. Skip plain 5W-30 off the Walmart shelf.
The oil filter on the Buick 225 is a Wix 51258 (or equivalent). The AMC 258 takes a Wix 51515 — the same filter the 4.0L XJ uses, which makes finding one trivial at any parts store. Hand-tight is the spec for both; an oil-filter wrench is for removal, not installation.
| Part | Vendor | Est. price |
|---|---|---|
| Wix 51515 oil filter (AMC 258 / AMC 304) | Wix | ~$9 |
| Wix 51258 oil filter (Buick 225 Dauntless) | Wix | ~$11 |
| Valvoline VR1 Racing 10W-30 (high zinc, flat-tappet safe) | Valvoline | ~$9 |
| Rotella T4 15W-40 (high ZDDP, flat-tappet safe) | Shell | ~$6 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.