Video on Toyota D-4S Direct Injection System(new for 2023 Prius) and does it work

While the gen4 Prius never got it, Toyota introduced their D-4S direct injection system back in 2015 on some Lexus models and in 2017 on some Toyota models. Direct injection-only engines get better power, fuel efficiency and lower emissions than port injection-only, but they suffer from much worse carbon buildup on the intake valves. With some manufactures(looking at you Mazda, Audi, & BMW) and driving habits, you can need valve cleaning every 40k miles or less.

Toyota's and other manufacturer's solution has been to use both direct and port injection together to reduce carbon buildup but still get most of the direct injection advantages. The disadvantages to these systems are the added complexity and cost, as well as a potential increase in maintenance costs if the system isn't reliable.

Now that the updated D-4S system has come to the Prius for the 5th gen, it might be worth looking at how well it's worked on previous Toyota models. The video is about a 2017 Sienna with 80k miles, but most of the content applies to new gen5 Prius owners as well.

Key takeaways:
- The system works - 80k miles, very clean intake valves
- Mild reliability issues to start(mostly with the early direct injectors), but the bugs are mostly worked out by now.
- High quality fuel is important with the high-pressure direct injectors; use Top Tier branded gas.
- If the system ever needs servicing, make sure your mechanic is experienced with the Toyota system; there seem to be a lot of details with things like seals and matching and non-reusable parts that could trip up an independent mechanic if they're not knowledgeable and careful.
- The direct injectors are expensive. A gen5 Prius will have four direct injectors at roughly $485(MSRP) each, and four port injectors at $225 each. (I got the prices from the Corolla Cross which uses the same M20A family engine). The high-pressure fuel pump is even worse at $1270(MSRP). If you have a major failure of the direct injection system when you're out of warranty, you could be looking at a mid four-figure repair bill. Moral of the story: USE GOOD FUEL!!!