| Engine oil & filter | M176 4.0 twin-turbo · MB 229.5 · 2.4 US gal (9.0 L) with filter (2018 G-Class manual, G 550) | Now, then when the ASSYST service interval display calls for it (owner's manual) | The 2018 manual, which also covers the 4×4², lists MB 229.5 for all models. FCP Euro lists its 9-litre 229.52 kit and the Mann filter kit for the G 550 4×4². Check that whatever oil you use carries an approval your manual allows.Liqui Moly Top Tec 0W-30 (MB 229.52) oil change kit, 9 L — listed for G 550 / G 550 4×4² · FCP Euro ↗Mann oil filter kit 176 180 08 00 (M176) · FCP Euro ↗ |
| Air filters | M176 air filter set | Now if undated | Dusty trail use loads the filters quickly.Genuine Mercedes air filter set 177 094 00 04 (M176, 2016–2021) · FCP Euro ↗ |
| Cabin air filter | W463 cabin filter | Now, then yearly | Mahle LAK120 cabin air filter · FCP Euro ↗ |
| Spark plugs & coils | M176 spark plugs (Mercedes-spec) | Now if no record confirm in manual | Pulling the coils means removing the engine covers; read the misfire counters first.Genuine Mercedes spark plug 000 159 05 00 (M176) · FCP Euro ↗Genuine Mercedes ignition coil 177 906 02 06 (M176) · FCP Euro ↗ |
| Coolant | MB 325.6 (FCP Euro lists Genuine Mercedes for the 2015-on G 550) · approx. 14.9 US qt (14.1 L) (2018 manual, G 550) | Now if undated | Check hoses and the expansion-tank cap while you’re there.Genuine Mercedes coolant, MB 325.6 (pink), 1 gal · FCP Euro ↗ |
| Automatic transmission (7G-TRONIC PLUS 722.9) | MB 236.15 (blue) | Now if no record confirm in manual | No dipstick: new filter and pan gasket, then set the level at temperature with a scan tool.Genuine Mercedes ATF, MB 236.15 (blue) · FCP Euro ↗Febi 722.9 transmission filter kit · FCP Euro ↗ |
| Transfer case | Fluid type and capacity confirm in manual | Now if no record | Same two-speed case and centre lock as the G 550. |
| Front & rear differentials | Gear oil type and capacity confirm in manual | Now if no record | The portal axles come from the G 63 AMG 6×6 — don’t assume standard G 550 capacities. |
| Portal hub reduction gears | Oil type and capacity confirm in manual | Now if no record | Each wheel has its own gear set. The 2018 G-Class manual tells owners of the 4×4² to change the axle differential and portal transmission oil after a 2,000-mile (3,000 km) break-in period, so ask for proof it was done. Check every hub for weeps and compare the oil from each corner. A dealer that has done one before is worth finding. |
| Diff locks | Inspection — engage centre, rear, front in order | Now, then monthly exercise | Disuse kills lockers. If one won’t engage, trace vacuum or wiring before suspecting the differential.Vacuum hoses listed for the G 550 · FCP Euro ↗ |
| Power steering fluid | Type confirm in manual — MB 236.3 on earlier hydraulic W463s | Now if dark or no record | Never mix power steering fluid with ATF. |
| Brake fluid | DOT 4 Plus (Genuine Mercedes) · MB approval 331.0 (owner's manual) | Now, then every 2 years confirm in manual | At 6,694 lb on 22-inch wheels, the brakes work hard — start with fresh fluid.Genuine Mercedes DOT 4 Plus brake fluid, 1 L · FCP Euro ↗ |
| Drive belt | M176 accessory belt | Inspect now; replace if cracked or undated | Continental accessory drive belt (M176) · FCP Euro ↗ |
| Tires, dampers & battery | 325/55R22 tires · dual springs with adjustable dampers · group 49 AGM battery | At purchase | Check the tire date codes — replacements are big and expensive. Look for leaking dampers at all eight units. Load-test the battery: these trucks often sit for long periods.Bosch S6 AGM battery, group 49 · FCP Euro ↗ |