When we first heard that Mazda had cleared the major hurdles on gasoline compression ignition, and were just tidying up the details with clear production intent, the first kneejerk thought was: That's it for Mazda's consumer diesel . In particular, the Skyactiv-D that was intended for sale in the U.S., only to be delayed for years by various regulatory roadblocks and other issues that Mazda is frustratingly (but understandably) vague on. At least, it'd die out at some point down the road once Skyactiv-X was widely available.It turns out that's not the case at all. Mazda will adopt an approach that becomes more and more electrified and diverse the closer you get to 2035. But internal combustion will play a deep and central role up to that point, and probably beyond. Before we get to what those different powertrains, diesel and electrified, will look like down the road, let's stop and think about Mazda's philosophy.It couldn't be more different from the approach of most manufacturers that are currently producing BEVs and hybrids , which are heavily incentivized by both the automakers and the government, both state and local, depending on the locality. Even with all that cash on top of the hood, the market penetration of electrified vehicles is low. Mazda's too small to lose money paying people to drive EVs and hybrids.Its risky solution (which is plucky, but has had mixed results) is to simply improve the internal combustion engine. It's achieved the best fleet average fuel economy in the U.S. already, using a range of direct-injection gas engines that are mostly naturally aspirated. A few tiny nods to electrification have been introduced, like i-eLoop regenerative braking and the Demio EV (a Japanese-market, last-generation Mazda2 with a 20kWh battery that was tested with a tiny rotary engine range extender). But the focus is on combustion, not electricity.And that focus isn't going away anytime soon. Mazda believes that pure gasoline, gasoline hybrid, and gasoline PHEV vehicles will remain the vast majority of vehicle sold through 2035. At that point, Mazda forecasts, BEV and fuel cell vehicles should make up about 15 percent of the total of Mazda's lineup. The remaining 85 percent will utilize some form of internal combustion engine. Now, that includes hybrids and even a small number of CNG/LPG cars. And these are global numbers, as well. There may be even fewer fuel cell and CNG/LPG vehicles sold here than abroad.The reason Mazda thinks it can rely almost solely on fossil-fuel combustion for so long is the remarkable gains in efficiency it has made in the past few years. Skyactiv-G direct-injection gasoline engines were introduced in the Mazda3 in 2012; it beat its same-displacement predecessor by a not-insignificant 7 mpg highway/4 mpg city, thanks in part to a more efficient transmission that was part of the overall Skyactiv chassis and powertrain technology family. Basically, the 2012 Skyactiv engine was 15 percent more efficient than the MZR it replaced. The new Skyactiv-X engine is a further 20-30 percent improvement to Skyactiv-G, Mazda claims.And here's the part Mazda is betting on: Starting with these very efficient combustion engines means when it finally has to turn to real hybrids, the benefits will stack. Mazda's Dave Coleman, at a backgrounder briefing on Skyactiv-X technology, said that hybrids can leverage all of the internal combustion efficiency gains.Also, the per-unit cost of high-efficiency gas engine componentry seems to be less than the cost of adding hybrid technology to an individual vehicle. So says Mazda. This may be an assessment of the total lifecycle of developing the technology; if you're starting from scratch, the R&D, tooling, and so forth will make each unit extremely expensive until the costs are amortized and the production processes scaled up. So when Mazda says it's cheaper for the company to focus on improving the internal combustion engine, that may be true ... for them. And were they to form a technological partnership with a company that has expertise in electrification ( Ahem ... cough ... Toyota. - Ed. ), the unit cost assessment might flip entirely.Some of this future is coming sooner than you might think. Skyactiv-X arrives in late 2019, barring any hiccups. So too will a mild hybrid-electric vehicle and a BEV. The BEV is probably going to spring from Mazda's technical partnership with Toyota , and since the companies seem likely to want to both reap the benefits of such a partnership, the Mazda2/CX3/Yaris iA platform already co-produced by the companies seems like a logical bet. No one at Mazda is saying a peep about the particulars yet. But with so little BEV experience, and already investing R&D dollars into Skyactiv-X and rotary engine tech, Mazda's almost certainly stretched too thin to turn up a nose at Toyota tech.Yes, we said rotary. The Demio EV's little 330-cc range extender, a single rotor unit, will likely inspire a rotary engine range extender option in the BEV (you can see the patent drawing below). That may be Mazda's contribution to the Toyota partnership. It could also be that Mazda will license the Skyactiv-X's SPCCI combustion process to Toyota. Mazda is on the record saying that as long as an arrangement is in the best interests of both companies (that is to say, Mazda's getting something equivalent out of the deal), anything's on the table. So don't expect them to simply sell it to anybody who wants to put SPCCI in their cars.Finally, let's turn to diesels of the Skyactiv-D variety, the same engines we thought might be supplanted completely by the new Skyactiv-X technology. Mazda has assured us, through its engineers and spokespersons, that Skyactiv-D is coming to the U.S. The regulatory hurdles it faces are unclear, but it seems likely that given the egg of the faces of the agencies that didn't catch Volkswagen cheating are eager to stay clean. That is to say, there's extra scrutiny facing any new diesel application. It's also no secret that Mazda had to switch emissions reduction strategies midstream. After trying to avoid a urea-injection NOx reduction system, Mazda realized they couldn't tune Skyactiv-D to meet emissions without one unless they neutered its power and responsiveness. That wouldn't do, for a Mazda. So, given the VW headwinds and the urea-injection switch, some of the delay makes sense.Forget about sunk costs, too. It's part of the broader strategy to sell diesels here, as it is for other automakers. The sudden influx of light consumer diesels may seem bizarre in the wake of the high-profile VW scandal, but there's solid economics and consumer research supporting it. And beyond the current generation, Mazda promises to develop a second-generation Skyactiv-D engine that's more efficient than the current one, which is itself about 20 percent more efficient than the MZR-CD engine it replaced.There are a few hints about what Skyactiv-D gen 2 will entail. Certainly the Skyactiv-X technology may play a role — the careful computing that optimizes combustion for every single combustion event could make diesel combustion more efficient. Much of Mazda's plan is still secret, but we do know that one piece of the puzzle is more homogeneous charge. Another is friction reduction. And lastly, Mazda hopes to make the combustion process more adiabatic — that is to say, with less heat loss. Remember, energy converted to heat is energy that's wasted by not doing work exerting force on the piston.We'll see Skyactiv-D gen 2 in 2020, about the same time that Mazda's BEV shows up and just before its PHEV. Mazda is even considering diesel hybrid and PHEV vehicles as a very small part of the product mix, a vehicle likely to achieve truly staggering fuel economy.The bottom line is: Everything's on the table, however unlikely, but a few things in this scattershot approach are definitely greenlit and on the way. And there don't appear to be any roadblocks preventing Mazda from leveraging its Toyota technical partnership to get a jump on EV tech. But it's all dependent on internal combustion playing a major role for more than a decade. In this, it seems Mazda is being realistic rather than placing bets on a specific technology jumping to the forefront to replace internal combustion. That's a bet Mazda can't afford to lose, so it won't even play that game.