Are Honda's woes masking Renault's troubles?

For much of pre-season testing so far Red Bull-Renault has flown under the radar, logging a decent but not spectacular number of laps, and setting a decent but not particularly spectacular pace.

Other than a couple of niggly problems with the new Renault engine on day one at Barcelona last week, and a subsequent exhaust issue on day three, Red Bull enjoyed a relatively trouble-free first test.

The mood inside the team seemed one of quiet confidence - the RB13 looks a decent car and the Renault engine is felt to be a decent step forward. Those early niggles were not expected to be life-threatening, and team boss Christian Horner said he was impressed by the work Renault did over the winter.

Sure, Mercedes and Ferrari completed way more laps, and set faster lap times, but as Daniel Ricciardo pointed out, Red Bull never expects to do 150 laps per day like Mercedes often does. Red Bull never tries to "win the winter world championship", as Horner puts it.

But when you look across the full spread of Renault-engined teams, things have not exactly run smoothly so far. At some point there have been engine problems on all three Renault-powered cars, all serious enough to require time-consuming engine changes.

Red Bull suffered on day one; Toro Rosso lost all of day four; the works Renault team changed engines on the last day of the first test, and again on the first day of the second test.

That has to be cause for concern.

Sure, this is nothing like the unmitigated disaster going on at McLaren-Honda, but it is troubling nonetheless. One Renault insider even admitted Honda's woes were helping take the focus away from the French manufacturer's own troubles.

These troubles reared their ugly head in a significant way on day six of testing at the Barcelona circuit.

Max Verstappen completed 102 laps for Red Bull - the first time the RB13 has clocked more than a ton on a single day of pre-season testing so far in 2017.

But the Dutchman suffered an MGU-K problem in the morning, which required Red Bull to change the engine during the lunchbreak. Verstappen eventually returned to the track in the afternoon to attempt a Renault-powered car's first full race simulation. All appeared to be going well, until the car broke down again - "two laps short of a race distance" Verstappen reckoned.

Autosport understands Red Bull's recurring day six problem relates to the insulation on the MGU-K unit in the ERS, for which Renault has introduced an all-new design this year as part of a major overhaul of the entire power unit, in conjunction with technical partner Infiniti.

As it stands, the feeling inside Red Bull is that Renault faces no fundamental design flaws - that it knows it can fix these glitches in time for the first race in Australia. This is not 2014, when the Renault engine was blowing up for fun, or '15, when Red Bull and Renault fell out publicly over a serious lack of performance.

But Red Bull also felt confident it could do a race distance before Verstappen's car ground to a halt...

"I always stay very positive and try not to think about it too much," said Verstappen when asked if he was worried by these Renault failures. "That's what testing is for: to challenge all the parts, and to see how good they are and where you can improve."

But the aim is for those parts not to fail under the strain. Mercedes-powered teams have racked up 1865 laps over six days of testing so far; Ferrari teams 1764 (including Sauber with the 2016 unit); the Renault teams only 1299.

Red Bull's sister squad Toro Rosso arguably endured a worse first week of testing than the much-maligned McLaren-Honda outfit - logging 25 fewer laps across the first four days of pre-season running.

The second week has started better for STR, but there is concern at needing to run the engine in a detuned state to protect reliability. On top of this, the team is also battling its own problems on the chassis side.

"There's always something, either with the hydraulics or with the engine that is stopping us," explains Carlos Sainz Jr, who said he was "definitely" concerned by the new Renault engine's fragility. "A lot more minor issues compared to last week, that were just engine failures.

"It's something Renault is working on, on the reliability side. You can imagine in four days [between tests] there is not much you can change inside a Formula 1 engine, but they have adapted to the issues correctly, they have come in with precautionary solutions for this week of testing, to allow us to cover our programme.

"It's better for us, for all of us, but it's still the main point where they need to focus for sure."

Sainz says Toro Rosso must also shoulder a degree of blame for the problems it has faced so far, and reckons the lack of understanding it has of the potential of its new car is likely to prove more of a hindrance to the team's chances in Melbourne than any potential gremlins left in the Renault power unit.

"On Toro Rosso's side we are also having some problems - it's not all Renault's fault," he adds. "The positive thing is that we are doing a lot more laps than in the previous test, so today we could get into a rhythm a bit.

"In my opinion, the main concern for Australia is still not the reliability, it's that we can still do the rest of the huge amount of things that there are still to test on the car before Australia, and that we arrive to Australia prepared.

"On the Renault side, it doesn't depend on us, it's just pure luck if it works or not, if it breaks down or not. It's not our main worry - we need to focus on developing the car that we've created for 2017, and at the moment we still have a lot of catch-up to do."

As does the works Renault team, which lost Tuesday morning's running to a precautionary engine swap, and had to interrupt Jolyon Palmer's planned Wednesday afternoon race simulation thanks to what he described as a "persistent hydraulics issue".

He said this was not related to the engine, but Palmer reckons the power unit problems that have surfaced are to be expected given the extent of Renault's winter overhaul.

"We kind of expected we'd have some issues, but also the performance is improved compared to the other teams," he argues. "At the moment we're taking a little bit of pain, but hopefully in a few races' time we can get the reliability sorted and we can get more performance.

"I'm still happy Renault have done this because where we were last year with the engine, the potential was limited to a certain point. The reason we've taken a step back in terms of reliability is because the potential is a lot more.

"Obviously it's not been ideal, the reliability, but you kind of have to take one step back to take a few forward."

But that logic can only carry Renault so far. Mercedes and Ferrari seem to have made steps in performance without introducing so many fresh reliability worries, and their teams are able to log huge numbers of laps as a result, gathering all the valuable data and extra understanding of new cars, built to new rules, that extra reliability brings.

McLaren-Honda has taken a big step backwards because it cannot extract any extra performance from its new engine without suffering a catastrophic failure. Renault is nowhere near that level of disaster, but these niggling and persistent reliability problems are bound to be limiting the current potential of its new design.

So Red Bull and the other Renault-powered teams are stuck in a holding pattern - waiting for the manufacturer to deliver the fixes that will allow them to properly discover how fast their new cars can really go.

At the moment it feels like it could go either way, but Red Bull seems confident Renault understands the problems and will be able to fix them in time.

Its title chances rest on that faith not turning out to be misplaced.