DIY Oil Change: Mercedes-Benz R170 SLK Guide

Maintaining your Mercedes-Benz R170 SLK is key to its longevity and performance, and one of the most fundamental tasks you can undertake is a regular engine oil change. While it might seem daunting, changing your own oil is a straightforward process that can save you a significant amount of money and give you a deeper understanding of your vehicle. This guide will walk you through every step, ensuring a smooth and successful DIY oil change for your beloved R170.

Before you begin, gathering all your tools and materials is paramount. Preparation not only makes the job easier but also ensures you have everything at hand when you need it, preventing frustrating pauses. Remember, safety always comes first when working under a vehicle.

Essential Tools and Materials Checklist

Having the right equipment is crucial for a hassle-free oil change. Here's what you'll need:

• New Engine Oil: Approximately 8 quarts (or 8 litres) of Mobil 1 0W-40 is highly recommended for the R170. Always consult your owner's manual for precise specifications.
• New Oil Filter: A MANN HU-718/5X filter is specified for the R170 (and R171) and importantly, it comes with the necessary O-rings for the filter housing.
• Vehicle Lifting Equipment: A pair of sturdy car ramps (preferred for oil changes) or a hydraulic jack and jack stands. Avoid using the emergency jack supplied with the car for this task.
• Socket Wrench: A standard ratchet wrench.
• Drive Socket #8: For the oil pan lower cover fasteners.
• Drain Pan: A large capacity drain pan, ideally 10 quarts or more, to collect the old engine oil.
• Funnel: For pouring new oil into the engine.
• Empty Containers: Two one-gallon (or four-litre) jugs for transporting used oil for disposal. Old ice tea jugs work perfectly.
• Newspapers/Cardboard: To protect your driveway or garage floor from spills.
• Magnetic Cup: Invaluable for keeping track of removed screws and fasteners.
• Gloves: To protect your hands from oil.
• Shop Rags or Paper Towels: For cleaning up any spills.

Getting Started: Preparation and Safety

Safety is paramount when working under any vehicle. Always ensure your car is securely supported and cannot move unexpectedly.

1. Warm Up the Engine (Slightly): Drive your car for a few minutes to bring the engine oil up to operating temperature. Warm oil flows more easily, allowing for a more complete drain. However, be cautious; the oil will be hot.
2. Position the Vehicle: For an R170, using car ramps is often the safest and most convenient method. Drive the front wheels onto the ramps, ensuring they are properly seated. If your driveway has a slight slope, positioning the car so the drain plug is at the lowest point will aid in a more complete drain. If using a jack and jack stands, ensure the car is lifted evenly and securely on all four points, or at least the front two, with the handbrake engaged and wheels chocked. The vehicle must be on an even keel for accurate oil level checks later, but for draining, a slight tilt towards the drain plug is beneficial.
3. Access the Oil Pan: The R170 has lower covers that protect the oil pan. Locate these covers and use your drive socket #8 with a ratchet wrench to undo the fasteners. Carefully remove all bottom covers and place the screws in your magnetic cup to prevent them from getting lost.
4. Prepare for Drainage: Lay down a generous layer of newspapers or cardboard directly under the oil pan area. Position your large drip pan on top of this, and then place your 10-quart drain container on a 4-inch stand directly underneath the oil drain plug. Ensure you have your empty gallon jugs and funnel nearby.

Draining the Old Engine Oil

This is where the dirty work begins. Be prepared for a steady flow of oil.

1. Loosen the Oil Filter Cap (Slightly): Before you even touch the drain plug, it's a good practice to loosen the oil filter cap by about 1/8th of a turn. Sometimes these caps can be quite recalcitrant, and it's much easier to break them free while the engine is still intact on the ground. This also helps with the oil draining more smoothly by allowing air into the system.
2. Locate and Open the Drain Plug: Position your drain pan directly beneath the oil drain plug, which is typically located at the lowest point of the oil pan. Using the appropriate socket (often a 13mm or 17mm, though not specified in the source, it's a common size for drain plugs), carefully loosen and then remove the drain plug. Be ready for the oil to gush out.
3. Monitor the Flow: As the oil drains, the arc of the stream will change. Make sure your drain container is constantly positioned to catch all the spent oil. Allow ample time for the oil to drain completely; this can take 15-20 minutes, especially if the oil was warm.

Replacing the Oil Filter

While the old oil is draining, you can turn your attention to the oil filter assembly.

1. Remove the Oil Filter Assembly: The R170 uses a cartridge-style oil filter. The plastic filter assembly (housing cap) will need to be unscrewed. Remember, you already loosened it slightly in an earlier step. Carefully unscrew the entire assembly.
2. Disassemble and Replace O-Rings: Take the plastic filter assembly to a clean table. Gently disassemble it. The MANN HU-718/5X filter comes with new O-rings. It is absolutely crucial to replace all the old O-rings with the new ones provided. There will typically be a large O-ring for the main housing cap and smaller ones for the central stem. Be incredibly gentle when removing and installing these; replacements for the entire plastic assembly can be costly, around £60. Lubricate the new O-rings with a little fresh engine oil before installation to ensure they seat correctly and prevent pinching.
3. Install New Filter Cartridge: Place the new filter cartridge into the plastic assembly, ensuring it fits snugly.
4. Reinstall Filter Assembly: Carefully screw the new filter assembly back into its housing on the engine. Do not over-tighten! The surfaces mate on the O-rings, and only enough torque is needed to hold it in place and prevent unscrewing. Playing 'Godzilla' with the wrench can easily crack the plastic housing.

Refilling with Fresh Oil

Once all the old oil has drained and the new filter is in place, it's time to add the fresh oil.

1. Replace the Drain Plug: Ensure the old drain plug washer (if applicable, though often integrated) is in good condition or replaced. Carefully screw the drain plug back into the oil pan. Again, do not over-tighten; it just needs to be snug enough to prevent leaks.
2. Add New Oil: Remove the engine oil filler cap (usually on top of the engine, clearly marked). Place your funnel into the filler neck. Begin by adding about 7 quarts (or 7 litres) of the Mobil 1 0W-40 engine oil.
3. Initial Leak Check: Before replacing the bottom covers and driving off the ramps, do a quick visual check for any immediate leaks around the drain plug and the oil filter housing.
4. Lower the Vehicle: Carefully drive the car off the ramps or lower it from the jack stands. Ensure the car is on a level surface.
5. Start and Idle: Start the engine and let it idle for a few seconds. This allows the new oil to circulate throughout the engine and fill the oil filter. Do not rev the engine.
6. Shut Down and Wait: Turn off the engine and wait for about 5-10 minutes. This allows the oil to drain back into the oil pan, giving you an accurate dipstick reading.
7. Check Oil Level: Pull out the dipstick, wipe it clean, reinsert it fully, and then pull it out again. Check the oil level. It should be between the 'min' and 'max' marks. Add small amounts of oil (e.g., half a quart at a time) and recheck until the level is at or near the 'max' mark, but do not overfill. For the R170, a total of 8 quarts is generally sufficient to reach the full mark.
8. Final Covers: Once you are satisfied with the oil level and there are no leaks, reinstall the oil pan lower covers using your magnetic cup of screws.

Disposing of Used Oil

Proper disposal of used engine oil is crucial for environmental protection. Never pour it down drains or onto the ground.

Pour your collected used oil into the empty gallon jugs you prepared earlier. Many auto parts stores, garages, and even supermarkets like Wallmart (as mentioned in the source for the US, check local regulations for the UK) offer free used oil disposal services. Simply take your sealed jugs to a designated collection point.

Benefits of DIY Oil Changes

Beyond the cost savings, performing your own oil change offers several advantages:

• Cost-Effectiveness: You save significantly on labour charges.
• Quality Control: You choose the exact engine oil and oil filter that goes into your car, ensuring high-quality components.
• Understanding Your Car: It's a great way to familiarise yourself with your vehicle's underside, potentially spotting other issues early.
• Satisfaction: There's a certain satisfaction in knowing you've performed essential maintenance on your own car.

Frequently Asked Questions (FAQs)

How often should I change the oil on my Mercedes-Benz R170?

Mercedes-Benz generally recommends oil changes every 10,000 miles or once a year, whichever comes first, for modern vehicles. However, for older models like the R170, or if you drive under severe conditions (e.g., frequent short trips, extreme temperatures), more frequent changes, perhaps every 5,000-7,500 miles, can be beneficial for the engine's longevity.

Can I use a different brand of oil than Mobil 1 0W-40?

While Mobil 1 0W-40 is a highly recommended and popular choice for Mercedes-Benz vehicles, the most important factor is that the oil meets the specific Mercedes-Benz approvals (MB-Approval 229.5 or 229.3) as listed in your owner's manual. As long as the oil carries the correct approval and viscosity, it should be suitable.

What happens if I overfill the engine oil?

Overfilling can be as detrimental as underfilling. Too much oil can cause aeration (foaming) by the crankshaft, leading to reduced lubrication and potential damage to engine components. It can also put excessive pressure on seals, leading to leaks. If you overfill, you should drain a small amount until the level is correct.

Do I need to replace the drain plug washer every time?

It's highly recommended to replace the drain plug washer (crush washer) every time you change the oil. These washers are designed to compress and create a seal. Reusing an old, compressed washer increases the risk of oil leaks. Many new drain plugs or oil filter kits come with a new washer.

My oil filter housing is plastic; is it fragile?

Yes, the plastic oil filter housing on the R170 (and R171) is designed to be durable but can be prone to cracking if over-tightened. Always remember that the seal is created by the O-rings, not by extreme torque. Be gentle and use only enough force to snug it down.

Conclusion

Changing the engine oil on your Mercedes-Benz R170 SLK is a rewarding maintenance task that is well within the capabilities of most DIY enthusiasts. By following these steps carefully, prioritising safety, and using the correct tools and materials, you can ensure your R170's engine remains well-lubricated and runs efficiently for many more miles to come. Regular oil changes are the simplest yet most effective way to protect your engine's internal components and maintain its peak performance.

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